Ebay is a great way to start selling your products. The downside to ebay is that it is saturated with what I would call 'common products'. I am not sure if this is the correct phrase but by that I mean Electronics, Clothing, etc.
I think the most important thing about selling on ebay is to have a unique product as it is very unlikely that you will be able to undercut competitors in these 'common product' categories.
The thing I like most about ebay is that unlike on Google adwords where you have to pay for people to click onto your site, you do not have to on ebay. The other advantage on ebay is that everyone is on the same level, no ones takes favouritism over anyone else. This is great because it gives anyone a fair chance.
The best advice I can give on ebay is to have a clean, fresh and nice looking ebay page, and to carefully structure the keywords within your item description section as these keywords will determine whether you come up in a search. You can only enter a item description of around 60 characters so think carefully about what you are selling and what your customers are likely to search for when looking for a product like yours. For example if you are selling Goldfish, it may be worthwhile to use the keywords Goldfish and Gold Fish within your item description, as different people will spell it different ways and if you only enter Goldfish, and someone types in Gold Fish, guess what, they won't see your auction page. This is very important so spend some time seeing how others structure their item descriptions.
I hope this has helped!