Hi Davyd,
There is no strict requirement on how much you have sold or bought prior to opening an eBay store, but eBay recommends that you should have at least 25 or more listings prior to getting one! And Erika (eBay guru/SaleHoo member) also suggests that you sell on eBay for at least 3-6 months and generate around $500/month before opening your own eBay store.
To open a store all you need to do is -
* Have an eBay seller's account and your credit card placed on file
* Have a verified Premier PayPal account
I think you'll find these guides helpful -
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You may also try searching through the forum for more tips :)
By the way, may I ask what type of products are you interested in? We'd be glad to help you search for suitable suppliers. But please note that eBay is extremely competitive marketplace and it is quite common to find products selling at prices the same as or lower than wholesaler. WHY? Because a number of wholesalers (and dropshippers too!) sell on eBay.
Hope this helps :)