Always, and i mean ALWAYS...build your store first, if you advertise it with only 1 product then your going to turn down a lot of heads that have a look.
With products, lets say around 40-50, your going to have customers staying awhile, browsing through the store, see what you have, and even then may make a purchase.
Also work on contacting the customers as quick as possible with their products and say a thank you, which goes a long way to some people.
