If only one circuit request 10 gauge Romex (not 12), and if you can, use a plastic box that holds at least two and preferably 3 or 4 outlets so you have a place for every plug.
A larger multi gang (wall) box capable of holding additional outlets is smart, in case you add equipment. If you don't require additional outlets right now, fill the extra openings with a blank wall plate for about a buck.
There is essentially no difference in price between a single, double or multiple outlet gang box.
If your installing multiple outlets in one larger gang box, the electrician may allow a 30 amp breaker so it can support multiple 20 amp plugs. Then again, it may be against code. He can tell you what's legal and safe.
Again, best of luck with the project, dedicated electrical line are a marvelous bang for the buck improvement.