As a new seller you will be under severe limits on sales and restrictions on your account. Read the "new seller limits" on the site map, bottom of page for the rules and restrictions.
Having a store will not increase or remove the limits. You need to get some experience and gain ebays trust before even considering a store.
You also get up to 50 free auction listings a month without a store. They all disappear when you open a store.
Stores benefits include reduced listings fees (basic store listing fees are 20 cents vs 50 cents for non-store owners). That is about all the straight discounts you will get, so you will need to sell around 150 items a month for it to make economic sense.
There are other benefits, including better search visibility, but not much else.
Get some experience on ebay before you even consider a store. They are not a panacea for sellers.
Get up to 2,500 FREE listings* every month with an eBay Stores subscription
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