I used to sell on eBay back in the day — when you could make real money and the fees were far lower. There was no Paypal involved, and I actually received paper checks to bring to the bank as payment for my sales (yes, Virginia. There really was a time when eBay didn't own Paypal). I made great bank resell thrift shop tchotchkas and other vintage stuff. I had an eye for it, and supplies were abundant at thrift shop and flea markets. The bad economy killed this part of the business.
I stopped selling around the time when they made the rules so onerous for sellers, and the fees went sky-high. If you want to get into it and ship things yourself, I recommend buying small and easy to ship items.
There is a ton of competition in jewelry sales, but if you happen upon a good deal you should pounce. I had pretty good luck purchasing items at going out of business auctions. Two good deals I made were for Precious Moments figurines (ick!) and garden flags, those things people hang outside on a flagpole in the burbs. Easy to pack, and inexpensive to ship.
I have a few things to sell now, and not looking forward to getting on with it, but eBay is the only place I can get rid of a vintage Bakelite mah jong set and Stengl dishes.