I think you could tell by looking at my username.
I wouldn't be "evil" per se, by harming Pokemon or humans, but would accompany Team Rocket in domination over the common folk.
As to the other questions:
I would want to work my way up to be some sort of an admin. From what we know from the games, the admins just suck. Really.
What Pokemon would I use? I would probably have to have a Jynx, no doubt about it. And then a sprinkling of various Pokemon from my trainer card in my signature.