I have used fox farm potting soil with much success. I didn't even add any ferts (a bad thing) but i still made it all the way through a grow. I used stuff from lowes/walmart/etc but my first successful was with the fox farm soil. Cost like 15 bucks but is enough for a couple plants all the way. As for pot size I would say 3-5gallon using the biggest size that you possibly can. Also be sure to drill out some more holes for drainage, the more the better. Make sure to get some cloning gel/powder....makes cloning easier/more successful. :thumbsup:
good luck:smokin: