Every sale has its own page with the item, the buyer, the seller, the amounts and the status. Separate menu pages show the sales awaiting payment, to ship, shipped, completed and cancelled.
As your marketplace grows, you need to see which sales are stuck. The status pages show at a glance which buyers haven't paid and which sellers haven't shipped.
Every sale links to its commission and premium invoices, so you always know what you have earned.
Buyers and sellers handle their sales themselves in the members area; the admin pages are there when you need to step in.