I just bought some pretty cool wheels and motors for my future mobot!! I'm gonna make it some time next week. I hope I can do it.
Welcome! NiMh battery packs or phone battery chargers are the best for beginning.
Oddbot has made a cool tutorial here http://letsmakerobots.com/content/building-arduino-compatible-robot-scratch
Welcome to LMR Aegina. We look forward to seeing what you can make.