A good system would be a basic skills system like on a MMORPG that i've played called fairyland, where you learn skills like hunting, fishing, swordmaking, etc and as you level up those skills you can get better things from them, but you need something like wood cutting and metal working to make swords and both skills need to be of a certain level to learn swordmaking, and you can make better items than you can get from drops etc, or something like that.
What would also be good is something like you can only learn swordmaking if you're a warrior, potionmaking if you're a taoist and something for wizzies. And you have multiple skills, like Armour making as well.
You could also have it so that you can learn as many base skills as you like (e.g. Fishing, Farming, Wood Cutting, etc) and then you could learn 6 Apprentice skills (the skills like MetalWorking. These are the skills that you need for your Master Skills. you need 2 for each 1 master skill) and the you have Master Skills which you can only learn 3 of.