Hi There, i'm no expert on SEO but unless im very much mistaken (or your store is in a highly limited niche market) then without links onsite a search engine such as Google (which rates links incredibly highly) will bener rank your pages highly enough to make it onto the first few pages.
I am currently thinking of ways around this, perhaps by using links to other ebay sites/affiliates - not convinced its going to work though.
Unfortunately the days of simply entering a few keywords in the Meta tags html are long gone due to the over saturation of virtually every conceivable topic online.