Selecting products for e-commerce store

What’s up everyone,

I have an Instagram and Fb fan page focused on one of my favorite sports teams that I want to monetize with an e commerce store.

I want to physically stock my main products and supplement some dropshipped products that are available.

Whats the best way to select the products that I actually want to keep on hand? Would love some advice from Anyone that has a brick and mortar store or stock their own products! Thanks