iDigital is the best marketplace theme for WordPress
iDigital allows you to turn your store into a author marketplace. You can assign existing products to authors, or they can add and edit their own ones. Every authors will have a dedicated authors page on your site where they will be able to list all of their products, but they will also show up in your normal shop pages so you can sell your own products alongside those of your authors.
You can set commission for each author different or same commission if you like, reviews system, this theme also includes forums, blog & faq pages!!!