An Ebay store is for fixed priced listings only. You can accept best offers on your items therein. However, in order to get the best price a regular auction style listing is usually best. People like to fight for things. When they're just offered as a fixed price item, they oftentimes think it's overpriced and/or undesireable. That's because, in their minds, if it weren't, it would have been sold already.

EBay has become very problematic for new and established sellers alike. They have "listing limits" now. That is, a new seller just can't come along and throw 50 items for sale that have, for example, a cumulative value of $10,000. To begin they are only allowed to list a very low quantity of items with a low total value for the first month. You'll have to go to eBay's site and see what the exact limitations are. After 30 days you can ask for an increase in the limits and they will usually do it if you have good ratings.