Well pretty much anything you can buy for less and sell for a profit is good. If your trying to sell on ebay work more toward establishing your reputation then making a fortune. Buy items of low value that costs you pocket change and resell it for some small profits. Clothing is a steady market that most always generates small to decent income. You dont have to jump into the designer fashion market. But buy closeouts and liquidated stock and bundle a couple items into a lot and resell it.
I have found selling childrens clothes bundled into lots can be a profitable sale. Averaging 10 outfits that cost me on average a buck a piece to sell for $25.00 on average and sometimes up to $40 based on the type and brands. Sell 30 lots like this in a week and you can generate a steady flow of cash.
In the end its up to you to decide what to sell. Try selling items you like or know alot about. Or look for items you cant find on ebay. Most likely if your the one that puts them there then you have found a nich market where you can stand to generate a very nice profit stash.
Most of all dont give up. And if you have any problems dont hesitate to ask us here in the forums. There is always members in the forums. And most are very helpfull. If you have a question that has an answer then most likely a member will pick up on it easily and respond quickly.