Leatherwork depends a lot on what you want to make. I made a fur bikini for a friend's book launch once, and that wasn't very hard.

Minimum investment is a pattern, a piece of leather or fur, a leatherwork needle (which is triangular), and button thread or sinew. I strongly recommend adding a thimble though. If you want to work with hard leather, that's more challenging, because it's usually done with stamps and such so you need more tools.