These are the more essential quests in my opinion, for rewards you probably will really want.
Perils of Ice Mountain:
5 Farming, 5 Hunting, 5 Thieving.
You get the ability to smith pickaxes as a reward.
Buyers and Cellars:
No requirements, important to do if you want to train Thieving.
One of the rewards is the Thieves' Guild, which can be upgraded via a few increasingly difficult caper mini-quests.
The Jack of Spades:
No requirement except Diamond in the Rough. The reward is the southern desert city Menaphos.
Only requirement is 33 Quest Points and completion gives you the ability to wear rune platebodies.
Requires 31 Crafting and 36 Woodcutting.
Reward is access to Zanaris, being able to wield dragon longswords/daggers, Chaeldar for Slayer and being able to craft cosmic runes.
Tree Gnome VIllage:
No requirements except six logs.
You get the spirit tree tele-network as a reward.
The Dig Site:
25 Thieving, 10 Herblore Agility
You get 17.3k total EXP for this as a reward, but also the Codex Ultimatus and the Empty Throne; the latter is useful for training Mining, Agility and Divination and any of the three require level 65 before being able to train them there.
15 Thieving, 18 Slayer, 19 Crafting, 30 Ranged, 35 Woodcutting
Ava's device is one of the rewards here, which is useful if you want to train Ranged using crossbows. It'll usually attract and pickup your bolts so you don't have to, and has a lvl-50 variant if your Ranged is 50 before completing the quest and there's a lvl-75 variant if you complete Do No Evil.
The below are still very good quests with great reward but it's up to you on which you want to do or would do at your pace.
No skill requirements but requires The Grand Tree and Tree Gnome Village.
Reward is access to Ape Atoll, which has a mid-level agility course useful for training Agility, especially, especially 48 Agility and onward.
Requires The Restless Ghost, Priest in Peril, 25 Agility and 20 Cooking.
The reward here is the Ectofuntus, where you collect slime buckets, grind bones (or use ashes to skip that) and then worship the Ectofuntus to consume one and each and get x4 Prayer experience.
Creature of Fenkenstrain:
25 Thieving and 20 Crafting, also requires The Restless Ghost, Priest in Peril
You get the activated Ring of Charos as a reward, it's super useful for reducing pricing for a lot of services and also a lot of persuasion based dialogue branches.
10 Hunter, 30 Agility, 30 Crafting, 34 Agility
8.5k total EXP as a reward but also that the Penguin D&D may give extra penguin points.
One Small Favour:
Requires Rune Mysteries, Shilo Village and Druidic Ritual quests but also 25 Crafting, 18 Herblore, 36 Agility, 30 Smithing.
It's a bit long but you get 20k total EXP as a reward and a key ring to store your keys on.
Zogre Flesh Eaters:
4 Smithing, 8 Herblore, 20 Strength, 30 Ranged and 30 Fletching; also requires Big Chompy Bird Hunting and Jungle Potion
You get access to Jiggig with this quest's completion. You can kill the zogres for tomb keys and the locked coffins in the area can give fairly decent rewards, rewards both useful for training prayer and also just general profit.
Beneath Cursed Tides:
30 Attack/Strength, 30 Magic, 30 Mining, 30 Smithing, 30 Woodcutting, 30 Firemaking and 30 Cooking
The best reward here for this quest is the Giant Oyster (besides some nice lamps that give 20k EXP total), it's a monthly D&D where you feed the oyster, it'll open up and give you contents that pull from the treasure trail loot-table then it'll close until the monthly reset each month and it's rewards also scale with your total level.
40 Mining, 40 Smithing, 40 Crafting and 59 Magic
The reward here is the family gauntlets, which can swap between the chaos, cooking and goldsmithing versions if you speak to any of the three brothers. Cooking makes you less likely to burn food, the goldsmithing ones increase the exp of gold bars per bar from 22.5 to 56.2 and the chaos ones provide a 10% bonus to bolt spells.
As A First Resort:
Requires Zogre Flesh Eaters, 48 Hunter, 51 Firemaking, 58 Woodcutting
You get 45k total EXP for this as a reward but also access to the Oo'glog spa baths. They have varying really useful temp-effects, such as infinite run energy or boosted max-health + poison immunity.
Requires One Small Favour, Garden of Tranquility, 101 Quest Points, 66 Magic, 62 Cooking, 45 Smithing, 42 Firemaking, 40 Crafting.
You get a reward of 35k total EXP but also the ability to fish for raw Monkfish, which is a pretty useful mid-game food for healing.