Your real problem is that Ebay is awash with people trying to sell junk and make money, so you'd have to be kindof lucky to really make big bucks. Also you're not going to be able to make the big money until you've got a decent feedback rating (assuming you already haven't).
If you want to make money, you might want to try a different direction such as international finance like Zopa where effectively you become a loan company. �500 isn't going to make you a fortune, but it's more reliable than selling on Ebay, and you could reinvest your profit.
http://www.zopa.com/ZopaWeb/