At some point you start to learn how mobs (creepers, zombies etc) spawn and their various behaviors, which you can exploit to set up farms to automatically harv

At some point you start to learn how mobs (creepers, zombies etc) spawn and their various behaviors, which you can exploit to set up farms to automatically harvest their loot. Some farms are incredibly simple, and others very complex, but the end result is roughly the same. Some can be adapted to also let you farm experience for enchanting. Admittedly it can break progression a bit when you have enough of them but generally one or two well optimized setups can produce a fair amount of resources.