Hello Baki Hanma and Melody,
I have in my "expeditions across the internet" found quite a few sources saying that alchemy is simply a mental thing, and while yes maybe metal could be turned into gold by a VERY VERY advanced person, anyone who can think can practice a form of alchemy.
By "transmuting" the bad qualities of your person into good ones, you've just performed a basic task in mental alchemy. By say, "feeling" positive in a negative situation and then actually feeling positive, you've just performed a very useful bit of mental alchemy.
So, maybe after sufficient energy pathways have been developed, and realization of oneness and all those other pre-requisites are met, then maybe if we wish to turn metal into gold for no reason involving personal gain then we could. But for now, I can say I'm happy in always being able to feel positive, happy, and joyful, even when karma throws a curve ball at me.

Werp