The Auctiva store doesn't require you to have an ebay store. However you cannot stock it with items to sell outside of ebay as it's merely a "display" of your active EBAY listings: auction, fixed price, and ebay store items (if you have an ebay store). Its advantage is that if you have a number of items for sale at one time on EBAY, a buyer can link to your store and see all those items displayed at once. It is simply there to help promote your (ebay only) items, just like the scrolling gallery.