Welcome to modern newfags! If you are reading this then you are probably also a poorfag because this is the budget deck guide.
Before we get into it I want to first talk about what the modern format is.

In case you don't know, magic has different formats and each format has their own set of deck restrictions.
You have draft, pauper, standard, modern, legacy, vintage, and commander (there's more but these are the big ones)
All of those besides draft are constructed formats, which means you make a deck out of what you own and bring your own deck to the event.
Modern is a format that allows cards from 8th edition on that aren't on the modern banlist. Here is the ban list for all formats
https://magic.wizards.com/en/game-info/gameplay/rules-and-formats/banned-restricted

Average decks in modern range from a few hundred to 2 thousand dollars (don't worry the only deck that expensive is jund and jund isn't the best deck right now the rest of the decks are half that cost or less)
If you want a cheaper format pauper decks range from $20- $120 and do not rotate.
There is also standard but those cards rotate and if you are putting a deck together slowly your cards may rotate before the deck is finished. Also standard decks can be around $400 themselves and most of the decks I'm going to talk about here are going to hopefully be around that or less than that but these cards won't rotate so you don't have to worry about that. You will be able to play all of these cards unless they get banned but since these are budget options I doubt any will.


Why are modern cards so expensive?
Modern cards are expensive for a few reasons.
1. High demand- modern cards are pretty powerful and a lot see play in other formats like legacy, commander, and vintage. Modern itself is a popular format so the cards are pretty sought after.
2. Lower printing- wizards of the coast claim a lot that they don't reprint cards because they would be too powerful for standard. Whether or not you agree with this is on you but that is their official claim. So for a modern card to get a reprint it has to be reprinted in a set that does not go into standard and those aren't that common. We used to have modern masters every other year or so but masters 25 was a piece of shit and sold like shit so wizards thought no one wanted masters sets anymore. tldr; cards printed in low quantity drives up price

What is a budget deck?
For this guide we are going to consider a budget deck anything below $500 at the time of this guide being written so don't crucify me if a card shoots up in price and a deck is no longer budget. Now I know people are going to say "$500 is not budget! we want under $100" well guess what, when average decks in the format are 1k under $500 is pretty budget, if you can't eventually spend that, play pauper or on cockatrice or xmage
I will list some decks that are under $500 list a good place to start building the deck, future upgrades, and give you a rough estimate of what the budget version of the budget deck costs.
This guide is meant to be used at a starting point and these decks are meant to be upgraded so they may feel a bit weak at first.


What are some budget decks?
Burn- the best choice because the cheap version is good, the final version is relatively cheap, and contains some modern staples for other decks
storm- tier 1-1.5 deck, doesn't need fetches to run (fetches are some of the most expensive cards in modern) , and frequently does well in tournaments
Budget dredge- Dredge is fun, one of the most expensive cards in there is blackleave cliffs which make up about $200 on their own but you can build a version without them for under $500. Actually the full version of it costs just a little over $550
8 whack- cheap fun deck good for beginners
Budget 8rack- What I originally started with, it's neat but not very good at the moment
Merfolk- modern staple, can actually be upgraded to a legacy deck
uw spirits- new hotness
budget affinity- shares most of the cards with the full version, kind of weak right now due to a ton of artifact and creature hate
stompy- the go to budget deck, has gotten some new additions recently so it has improved a lot
soul sisters- mono white lifegain deck
death and taxes- really skill intesnive
scapeshift- very linear

Saffron olive from mtg goldfish likes to make budget decks a lot so i will link this page here. Just know that seth is a good player and a lot of his wins on his videos come from his experience. He also records good leagues he does so he may exaggerate how well a deck does. Also he sets these around a theme and most of these decks do not have modern staples so they can't really be upgraded to better decks.
https://www.mtggoldfish.com/metagame/modern#paper



Burn:
So there's 2 versions of burn
There's mono red burn which is the budget version and then there's naya/boros burn which is the full version
Good news is that they share most of the same cards.
Here is an example of what a full naya burn list looks like (Around $500)
https://www.mtggoldfish.com/archetype/modern-rw-burn-46478#paper
The full deck is over $600 in this list however there's a few changes you can make to lower the cost of the full version by a lot.
1. You don't need ensnaring bridge in the side. It is good but you don't NEED it (saves 90$)
2. since all of your fetchable lands are mountains, you just need red fetches. Just get more bloodstained mires instead of arid mesa's and you'll save another $100
As you can see the most expensive cards are the fetches, shocks, and goblin guides. The version below doesn't have any of those and can be build for around $70.

Mono red burn ($70)
https://www.mtggoldfish.com/deck/361505#paper
Here is an example of mono red burn. This list is a little old, I would add monastary swiftspear (don't worry she's super cheap) and 1 or 2 shrine of burning rage. A grim lavamancer would also be pretty good.
The downside? Not as fast as naya/boros burn, less sideboard options, and less consistent.
Upside? Cheap, still decent, and you'll just need some lands, goblin guides, and a few cheap burn spells to build the full version and you can do that piece by piece.


Storm (Around $420)
Here is a decklist for storm
https://www.mtggoldfish.com/archetype/modern-storm-46456#paper
The deck itself doesn't need fetches to run so it is fairly cheap. This deck does not need any upgrades.
That being said there isn't really any budget options besides swapping 2 barals for 2 more goblin electromancers but that only saves you $10

Dredge (Full version $650)
deck list https://www.mtggoldfish.com/archetype/modern-dredge-26688#paper
Budget options
Replace arid mesa with wooded foothills (save around $75)
replace thoughtseize with duress in the side (saves about $45 and does what you need it to do)
Replace blackleave cliffs with either more blood crypts or dragonskull summit (saves between $50-$90)
Replace 1 brutality with a 4th duress (saves $15)

Downside- you need bloodghast and life from the loam for the deck to function so there's not budget replacements
upside- you make those budget changes and you can make the deck for about $380

8whack ($240)
goblin deck that is supper cheap for the full version
https://www.mtggoldfish.com/articles/much-abrew-8-whack-goblins-modern
downside- no budget alternatives, very linear, just loses to some matchups
upside- fun, fast, and there's a ton of videos on it

8rack (full version $1,200)
Mono black discard deck
full version https://www.mtggoldfish.com/archetype/modern-8-rack-43491#paper
budget options
replace Liliana with necrogen mists (save over $400) and this card does what you mainly want lilly to do
replace thoughtseize with funeral charm or blackmail- save $60
replace collective brutality with wrench minds (save about $75)
replace urborg and mutavault with swamps and dakmoor salvages (save $130)
also dakmoor salvage has good synergy with raven's crime
Budget version comes to about $430 a big difference from 1,200

Merfolk (Full version about $350)
https://www.mtggoldfish.com/archetype/modern-merfolk-52845#paper
You can hold off on aether vials to save about $150
Replace them with a 4th harbinger, 4th cursecatcher, 2 seas claim. get vials whenever you can and each time you get one place it in the deck.
Really good deck because the youtuber Nikachu posts mainly merfolk videos so you can learn the deck fast.
downside- even the full version is tier 2 at best

UW spirits (Full version $650)
https://www.mtggoldfish.com/archetype/modern-wu-spirits#paper

Budget replacements
cavern of souls (replace with lands like glacial fortress, mystic gate, a 4th seachrome coast save about $340)
mutavault (replace with more moorland haunts save about $25) be warned that mutavaults make this deck way stronger and they aren't that pricey
Replace any super expensive creature with nebleghast herald and you'll be okay
Budget version will cost about $300


Budget affinity Around ($50)
http://tappedout.net/mtg-decks/19-01-18-affinity-budget/

Ways to upgrade
1. spire of industry
2. steel overseer
3. arcbound ravager
4. mox opal
just add these to the deck whenever you buy one to improve the whole thing


Stompy ($150)
https://mtgtop8.com/event?e=19804&d=327726&f=MO
You can cut a thrun the last trol for another scooze and save about $18

pretty decent deck. easy to learn. only a few of these cards go in other decks though

Souls sisters ($185)
https://www.mtggoldfish.com/deck/1142261#paper

You can save about $40 by replacing archangel of thune with restoration angel. Won't be as good but it has some decent synergy with the deck.

Death and taxes (full list says over $600 but we can get that way down)
https://www.mtggoldfish.com/deck/1012192#paper
1. I like this version better than black and white taxes because the mana base for bw is shit and will lose you games.
2. take out canopies and put in shefet dunes. this saves you $200 and gives you another land that can produce white and colorless mana.
3. You can also replace field of ruins (they aren't great in this deck) with eldrazi temples to let you play things like thought knot seer and reality smasher (if you do that replace 2 plains with the other 2 eldrazi temples so you have 4)
4. replace aether vials with aven mindcensors, thought knot seers, or even a reality smashers to save over $100

Scapeshift ($520 for full version)
https://www.mtggoldfish.com/deck/1245982#paper
1. replace verdant catacombs with windswept heat to save about $40
2. replace prismatic omen with another farseek and save about $28 or another scapeshift and save $13




I am sure there are more budget options but here's all I can think of at the moment.


Tips for newfags

1. Newfags generally think buying lands is worthless and don't understand why they are so expensive or why they are necessary.
They are needed if you run multiple colors to make sure you have the colors you need when you need it. lands that enter tapped are too slow. Plus they go into plenty of decks so you can buy a playset of fetches and use them in multiple decks. If you ever have extra money to throw into magic buy a fetch or shock land you don't have. Especially if it just got reprinted because they don't drop in price for long.

2. most modern staples see play in several decks. i.e snapcaster mage is in most blue decks and aether vial is in most creature decks. Investing in staples is good especially if you might end up changing your mind on what deck you want.

3. Don't like a deck you got? Trade it in! sure you'll lose some money but modern cards hold value well and a lot gain value over time.

4. Use the same sleeves for all of your decks so you can build new decks with your staple cards and you won't have to worry about changing sleeves

5. expensive card? sleeve it right away and even double sleeve it.

6. want to try out a deck before you buy? xmage and cockatrice are free and easy to use. also ask at your lgs to see if someone will let you use a deck for the night.