I've sold on eBay for over 11 years - in that time it's become harder &harder to make a living as eBay keeps changing the rules and raising its prices.
the ebook method described below has now been knocked out by eBay since they don't allow digital products.
so you need to find your niche & MOST important find your source of supply. I've sold many things over the years, but have come down to just 3 products now - Classics Illustrated comics, National Geographic maps & AH General magazines. I have a large stock with multiples of each item, so i save a lot of time by being able to relist the item just sold rather than having to create a new item.
re the feedback issue, you do need to gain some fdbk before you can sell, but people will buy from you if you're selling low $ items at first. Sell the DVD, not the DVD player!
there are a lot of other cost & time saving things you can do - guess i'll have to write a hub...