One roUGe's guide to ballin' on a budget

[wvhills]

but extra auction Slots can only be purchased with platinum? ...

yes that's right. You have to have plat to get extra auction and inventory slots. The best deal is buying an equipment bundle which costs 70 plat but you get 10 Auction slots, 25 or 50 inventory slots (I can't remember which), 3 pink equips and 25k gold. If you can't buy plat then you can do some free offers. It may take a few weeks but you can do enough of those to get 70 plats together.