MHINFO

WEAPON CRAFTING:
When you're making yourself new weapons, the order of importance of their stats should go like this:
Sharpness > Raw attack power > Poison /Blast/Slots > Element > Sleep Status/Paralysis Status
*  Not only does Sharpness prevent your weapon from bouncing, but it applies a sneaky damage bonus behind the scenes you can't see. Keeping your green sharpness weapon always at green will do way more damage than letting it drop down to orange or red before sharpening.
* Slots I'll discuss below in the armour section so we'll get to that. Their value is hard to gauge.
* Element is helpful, but it is not nearly as powerful as it is in Pokemon.  A weapon with great sharpness and great raw will always out damage a weapon with good sharpness, good raw and a good effective element.
* Poison is a great status. It's  powerful & viable in both solo and online play. A good rule of thumb though is that if you fight a monster, and find out (the hard way) that that monster can poison YOU, it won't take much damage from poison weapons. In those situations bring something else.
 *  Blast you won't come across until later (Brachiodos being the first monster that has weapons with it as an effect), but it has the same usefulness as poison in that it can be used against a lot of different monsters, whereas if you were making loads of elemental weapons, you would need to change them regularly between quests.
* Sleep/Paralysis have great applications in group play, or if you're using ranged weapons, they're less useful in solo play but can still be used to dish out extra damage.

WEAPON POWER:
Prior to X/Generations,  MH used a damage formula that isn't really worth explaining fully (and also I don't fully comprehend it myself) but essentially inflated the numbers of certain weapons to emphasise increased attacking power, but the "true" raw power was much lower and that was what was used for calculations.
Generations does away with this and just exposes a weapon's true raw power. What you see being called "motion values" are, essentially an expression of a given attack's percentage of that true raw power, slower weapons generally having higher motion values to compensate for the smaller amount of attacks you'll hit with. Faster weapons then, having lower motion values but hit much more often.
Each monster also has hit zones that will affect damage based on the type (impact, shot or cutting,) Rathian for example has a squishy belly but a tough head which will affect where you'll want to attack with various weapons.
When comparing weapons, generally, you can compare the attack powers of two weapons of the same type: A Sword and Shield with 140 attack power is stronger than a SnS with 116 attack power. That's fine. BUT you cannot compare weapons of different types.
ARMOURS:
So every big monster you kill can be made into armour, and these armours come in two types. Blademaster (Melee) and Ranger (Ranged). There is also a different armor set for each rank that a monster appears in, for example Nerscylla is the Low Rank armor; Nerscylla S is High and Nerscylla X is G-rank.
The ironclad rule here is that Blademaster armours have twice as much defense as Ranger armour, since they have to be up close to deal damage. And generally speaking, blademaster armour will have skills that benefit melee combat (sharper weapons, faster charge times on weapons that charge up) and ranger ones have skills more based reloading and shot recoil.
What armour you can wear is totally dependent on what weapon you use. You can't wear blademaster armour with a bow for example. The two exceptions are hats (any hat can be worn with any weapon), and the armour you start with.
SKILLS:
*Skills are baked into your armor, generally having 1/2, less commonly 3 and rarely 4.
*Any given armor piece or weapon can have from 0 to 3 Skill slots
*Talismans are essentially just extra equipment that can contain up to 2 skills, plus up to 3 slots.
*Some pieces of armor have a skill called "Torso Up" which doubles the skill points of whatever is equipped to your Torso slot, generally used in end game for mixed sets.

How Skills are Activated
Once you have your armor and talismans equipped you can see the skills on your Status screen and they are activated based on the points given:
* Between -9 and +9 skill points: Does absolutely nothing. This is something you have to really wrap your mind around if you've played a lot of other RPGs. If you have +8 attack power on your armour, that means your attack power has gone up by zero because +8 doesn't activate a skill.
* Exactly +10: Activates a skill (Attack Up Small, Halve Stun, and Gourmand)
* Between +11 and +14: no extra skill
* Exactly +15: Sometimes activates a higher level of skill (Attack up Medium, Negate stun and Scavenger)
* and so on with skills activating every 5 points up to 30 in certain cases.
*  -10 or less: Activates a "bad skill", like Attack Down small, being stunned for twice as long, or getting hungry twice as fast.(
DECORATIONS:
*These are the little trinkets that you put into your equipment slots to increase your skills. They can only be forged by the Smith, you will never find them in game or have them as quest rewards.
*They come in 3 sizes, 1 to 3 slots, with 3 generally being the best, but the hardest to slot in and 1 being the weakest but most versatile.
*Many have a negative skill associated with them, for example a Decoration that increases your Poison resistance also decreases your Stun resist, so be careful to balance these out (higher levels of  Decorations will generally offer more of the positive skill with less of the negative skill.) This is to stop people having completely overpowered armor sets as there are some skills that are impossible or near impossible to have together on a set.
*Watch out, the game's translators hate you and Decoration names don't correspond to skill names, and skill names don't correspond to the ability names - the Razor Jewel gives points in  Sharpness which activates the Razor Sharp skill, whereas the Handicraft Jewel gives points in Handicraft conveniently enough, however the skill it activates is called Sharpness+1 which, obviously can be easy to mix up.
*While in the Decorations menu you can view the Decorations by their skill name which will make them easier to find.
ELEMENTS
*Elements are far less important than you think, they're a nice way to get some extra damage, but good raw is almost always better unless you're building a specific element up set I wouldn't rely on them, plus it means you're using much needed resources to keep elemental weapons upgraded, which can seriously deplete you in early game.
*Element damage is applied in addition to your physical attack, based on a monster's weakness to that element and what body part you are attacking. It is applied every time, so weapons that attack more get more value from it. Element is much more useful on a weapon like Sword & Shield or Dual Blades than it is with a Great Sword. Elemental attacks are also subject to a Sharpness bonus.

On armor, again, element is less important than you may think but it does have some important points to note:
*for each point your amor has in an element it receives either a positive or negative damage modifier of 1%
*Like with skills, at certain thresholds you get either a buff or a nerf of your resistance to that element's corresponding blight. +10 meaning you'll only get the lower tier of the blight and +20 meaning you're immune to the blight.
*There are armour skills that can affect your elemental resistance by a certain number, but i wouldn't waste the slots on them. However if you have an armour set that gives you Element Resist down, i would recommend spending a slot or 2 to get rid of it.
*There are some kitchen skills that can increase your resistance to elemental attacks if you need them.
*A lot of monsters that are elemental, may only have 1 or 2 attacks that actually use that element, or use them sparingly, for example: against a Rajang, thunder resist isn't hugely important, but against a Khezu who spams thunder attacks all day, it's far more useful.
STATUS ATTACKS
* The main statuses are: Sleep, Poison, Paralysis
* Statuses are applied at random each time a weapon attack connects, they may not always proc (you'll see an affect when it hits), but this rate can be increased by skills such as Status Atk+ and Status Crit. Again, faster weapons are better as they have more opportunities to proc.
* Each monster has its own threshold for resistance, and each time that status is applied to the monster, it increases until it hits a maximum. To give a hypothetical: say you have a weapon that does 20 sleep each time it procs, and a monster with 100 resist, once you hit it 5 times with a status proc, it falls asleep. Then, the status is reset to 0 and the monster's resistance goes up by 100, which means the next time you want to afflict the status you'll need to hit it 10 times for it to fall asleep, eventually it reaches its max threshold of 600 and will go up no further and will take much more time to apply the status in future.
* Sleep causes the monster to fall asleep, naturally. While sleeping, the attack which hits a monster and awakens it will do 3 times the damage.  You want to save your big attacks for this, bombs being very useful as they do fixed damage. If you're playing with people using sleep, try to bring some bombs, and  pay attention, you don't want to wake a sleeping monster with a standard attack. The best way to tell if a monster is falling asleep is that the music will drop out, if that happens stop attacking
* Poison is a DOT effect, and will do a set amount of damage over a set period of time, all monsters can be afflicted, however some  have such a high resistance it's not worth even trying.
* Paralysis freezes the monster for a few seconds allowing you to get some extra damage in. Useful in groups as it can be used to trigger staggers or other statuses.
SORT-OF STATUSES
* These ones are edge cases so i'm covering them here
* KO is applied by hitting it on the head with impact weapons (Hammer, Hunting Horn, Impact Charge Blade Phials.) The monster will thrash about on the ground for a while, giving good opportunities for damage.
* Stun is similar to KO but is applied by using a Flash bomb on a monster. Monsters are usually immune to them while enraged though. Useful against flying monsters to drop them to the ground.
* Blast (Slime in 3u) is super powerful. It applies like the statuses described above, but when it reaches the threshold it causes an explosion. Great for doing location damage and getting breaks and just for doing lots of extra damage, useful against pretty much everything in the game. Technically a status but it's not affected by the Specialist kitchen skill.
* Mounting isn't really a status effect but the manner in which it is applied  is the same, usually your first mount will take 1 or 2 aerial hits, but with each subsequent mount it gets harder. Due to the changes in Generations it's far less powerful than it was in 4u for group play but still can be useful.
MONSTER STATUSES
* Statuses that monsters afflict you with are slightly different to how they work on the monsters themselves so i'll go over them here.
* Players don't have thresholds (except stun) and monster attacks that cause statuses will always affect you if they hit.
* Poison is still a DOT, there's also improved poison effects like Deadly or Noxious Poison that do even more damage. Tank the damage or take Antidote or Herbal Medicine
* Sleep makes you drowsy for a few seconds where you'll stagger around for a while before falling asleep. While you're asleep you can't affect how long it takes to wake up and you will take extra damage from the first attack. Players can kick you to wake you up. You have a few seconds before sleeping where you can take an Energy Drink which will negate the effects, the Felyne Insomnia kitchen skill also negates sleep.
* Paralysis works the same, you're stunned on the ground for some time until you're hit or just get up on your own.Thunderblight makes the effect last longer.
* Stun, you can be stunned by taking lots of attacks in quick succession or if a Gypceros uses its flash attack. Can be broken out of by spinning the stick and mashing B.
* Frenzy is given to you by frenzied monsters, it starts a countdown where you have to inflict enough damage before the bar fills up. If you do, you get a boost to affinity and if you don't you lose your health recovery (red health)
* Bleeding is caused by a few monsters, mostly Seregios. While afflicted you'll take massive damage while running or rolling. You have to eat meat or cure it by crouching for a short amount of time. Fairly easy to avoid but get rid of this ASAP.
ITEMS:
* Items are super important, they'll keep you alive, allow you to do much more than just attack, and are often overlooked in terms of importance compared to learning weapons or crafting gear.
* Most of the more useful items in the game can't be bought, they have to be combined. For this, you'll be using the farm/trader NPCS. How they articulate changes, but the main gist is: give them items, and you get more of that item at the cost of some points.
* You'll start off with very little options but you get more items that you can trade and more slots to trade for as you continue.
* Important items to farm are Honey, Bitterbug, Dragon Toadstool, Might/Adamant Seed, Sap Plant, Godbug
* These allow you to make some of the more useful Items such as High Potion, Max Potion, Catalyst, Demon/Armordrug and Lifecrystals/powder
* Other items that are important are Dash Juice, Pitfall/Shock Trap, Flash Bomb, Tranquilizer, Barrel Bomb and Farcaster
* Some items have multiple levels such as Mega Armordrug or Mega Dash Juice that have stronger effects, but are much more costly to make.

MISC STUFF
* If you like a weapon, use it, if you like an armor set, use it. For most casual play, this is fine, it won't affect you too much unless you're doing endgame stuff like Guild Quests or Deviant Monsters
* Most people will look down on it, but the Auto-Guard Talisman that you get at the start of the game has one particular use: If you equip it, you will always block when you can, this can be used to train yourself in how to time avoiding attacks.  Take an SNS or similar weapon and try to roll through attacks, the results you see will help you:
- Blocked attack: Rolled too late (not at all), autoguard had to kick in
- Rolled and didn't get hit: Perfectly timed, do this.
- Rolled and got hit: Rolled too early, i-frames wore off
*  Monster Roars can be blocked.
*  I like to use Hot or Cold Meat instead of Drinks, they have a twofold effect of Drink items and Meat items, useful if you want to save space for items. Same with Energy Drinks, Herbal Medicines etc.
* Do Arenas if you want to try out new weapons, they don't cost any resources and if you fail you lose nothing, they also are a good way to see how certain skills, items and weapons interact.
* Don't waste your time Minmaxing until you get to G-rank, concentrate on learning a weapon or 3 and learning the ins and outs of the game itself.
* If you need money, go to your item box and go through each monster part, sell them so that you round them down to the nearest 5 (if you have 27 rathian scales, sell 2 or 7 to round it down) this adds up to a lot of money over time and still allows you to keep a good stock of monster parts.