Building an estore... starting out with MarketPress.

I want many people to be able to sell their own items in my store - where I would like to them to almost set up their own storefronts. I will need to receive % commissions on their sales to support my work. I am not clear on whether I must setup a multisite or not!

Am I also better off using Pro Sites? What is the best theme to use to support marketpress?

I also want to set this up like a gallery, so is Studio better than the Gallery theme?

I also want to setup Ad space - should I use the Daily theme instead, or is there a plugin or widget I can use?