The Quests are pretty straightforward tbh. Grindy, but quite easy.
By the time you reach the 2nd Nether Island and the 9th Overworld Island, you should already have quite a good income.
- A Big Carrot/Sugar Cane/Melon (farm with silk Touch for 2k/melon) Farm (always crop with a high Fortune item since it triggers, but doesnt lose Durability)
- Mob Grinders (FractalCake has some amazing tutorials how to build several of those)
-XP farm with lv 30 Zombie Spawners
-A Pig Grinder ( i now have 52 pig Spawners falling though lava to their death)
These Things give me a lot of Ressources for All the quests.
A witch grinder is only necessary if you have the money to buy several lv 1 Spawners (100m/ea), building a big Platform for 50+ glowstone trees will make you complete the quest in 2 days if you visit the farm 3 Times a day (every 3 hours).
Also make yourself familiar on how Optimisers work and use them to your advantage to maximize your Ressource income.
Dont invest in any high Diamond Enchantments yet, stick with the Prot IV Iron Armor you got from the quest in the Overworld or, if completed, place a chest near the nether Portal with the infernal armor Set, Just in case you drop into lava or something.
PS : You can Set up a Grinder for the Magma Slimes and Normal Slimes in the Overworld ( 8x8 area. 5 Blocks high so they cant jump out, let water from the edges push them to 3 Block tall cacti with droppers below, this will still count for the quests ( Not the "kill lv 0 Slimes" quest from the overworld, though)