I primarily use BX Pro Mix with some perlite mixed in. I had to add perlite this year, because I couldn't find any Pro Mix HP which already has extra perlite. I also added bone meal, blood meal, dolomitic lime, mushroom compost, and Osmocote, and Garden Tone.
I'm not positive, but I believe the majority are in 15 gallon (could be 10, but I think they're 15). I believe the large pots are 25 gallon. I picked them all up second hand, and I can't find a size on them. That's why I'm not positive.