Gregbot3000

Hey all, I am new here (Thanks for this thread, its perfect for me). Just a question, The good tires I bought a few years ago have finally been used up. So now I would like to update the wheels as well. Help me out on sizing, specifically regarding the offset/Width, what are my limits here? I am not looking to go nuts with this thing, just a better look. But I do not want to make a poorly informed purchase. Any help would be great.