A professional looking Ebay & Amazon shop that's easy to list and manage

I currently have an eBay Shop that's not doing very well, I need the Shop looking professional, and the listing need to be easily uploaded ,and managed.

I would also like an Amazon shop which I could manage easily, additionally I have a Website that needs listings and managing, so if it could all be done in one management spreadsheet/database or software, or any ideas how i can achieve these tasks with a minimum of fuss and PC time would be good