The main place to find new schematics and tools are from loot chests. I need to scatter loot into chest around in locations where it makes sense to find treasure, as well as scale the rarity of different items according to the different chests.

Treasure locations, loot types and level target

Ancient city

Rarity: 60-120
Schematics: all
Parts: all
Gems:

Mineshaft

Rarity: 10-50
Schematics: pickaxe, handle
Parts: pickaxe, handle, binding
Gems:

Stronghold

Rarity: 30-70
Schematics: pickaxe, handle
Parts: pickaxe, handle, binding
Gems:

Pyramid

Rarity: 20-60
Schematics: shovel
Parts: shovel
Gems:

Jungle temple

Rarity: 20-60
Schematics: axes
Parts: axes, handles, wooden parts
Gems:

Pillager outpost

Rarity: 20-50
Schematics: weapon/sword schematics
Parts: blades and sword guards
Gems:

Swamp hut

Village

Rarity: 10-50
Schematics: All, in relevant
Parts: All, in relevant
Gems: Some, in relevant chests

Woodland mansion

Rarity: 50-90
Schematics: all
Parts: all
Gems: overworld

Ruined portal

Rarity: 30-80
Schematics: none
Parts: only gold
Gems:

Ocean ruin

Shipwreck

Rarity: 10-80
Schematics: all
Parts: all
Gems: some, overworld

Ocean Monument

Nether fortress

Rarity: 40-70
Schematics: all
Parts: all
Gems: some, and nether specific

Bastion Remnant

Rarity: 50-90
Schematics: all
Parts: all + golden ones
Gems: some, and nether specific

End city

Rarity: 50-130
Schematics: all
Parts: all
Gems: all

Spawners

Rarity: 20-50
Schematics: all
Parts: all
Gems: all

Loot drop from mobs

Zombies

Rarity: 10 - 50
Parts: all

Very slim chance

Pillagers

Slim chance
Rarity: 20-60
Schematics: all
Parts: all
Gems: none