hi,
The best place to start with will be a Magento bakend and then sell the same on ebay.. It is an advanced eCommerce system where you can manage your produts online with backedn admin, shopping cart, payment gateway and other notmal things that you migh t require,
or you can use eCommerce templates for the same, but you will not be able to sell on eBay. It depends on your requirements as well,
If you can tell the nature of products, I can give an outline of what best can be the solution,
Looking forward in anticipation to wokr on your projects,
Best regards,
Arun