To create a game like that first of all you need a lot of time, ideas, and to think techichal. Making any game isn't a walk in a park, sadly you have to look and work out every detail. But forget that for now hun, let try and get your idea going.

The first part you mentioned 'based economy and government) are normally see in RTS/Sim style game really. Automatically I think of the civilization games. So many have a look at that and other game similar to that, once you have a feeling how they work you can then start thinking how you can try and apply it to a RPG. Breath of fire game with the fairy village sort of has you looking after their economy to a small scale. So really just try and find game with element you want and see why you like then and why they work in short.

about the xbox 360 are you planning on making it yourself, selling your idea, or just as a mess around or many just for a portfolio? I'm just curious why your being pacific

I say keep your ideas to yourself, you never know when some sneaky bastard is going to come up and swipe your idea.

I have a few of my own, but (as stated above) i'm keeping it to myself...