In order to be any kind of successful on TCGPlayer.com you need to have a good sized inventory because getting nickel and dimed to death for one cheap card at a time is never going to get you anywhere and is often going to result in you losing money given how competitive the sales are and the shipping and fees involved.
So I made a few small sales where I think I actually lost money but the result was me being able to move up to the next and increase my inventory. This is going to go a long way in me being able to generate some more traffic to my page now.
On top of that, once I reach seller level 3, I can move up to 1,000 inventory items and so on from there. I think the highest is actually level 4 and at that point I think you can list as much as you want.
Needless to say this is a step in the right direction for me and I'm planning to fill up these extra 400 spots not asap to keeping things rolling.