Generally speaking it seems that Shopify is the most popular platform for quickly deploying a store and easily adding on features you need.

The steps are usually along the lines of:

- Pick a product/niche

- Pick a store name

- Build out a store website (on Shopify, for example)

- Run targeted ads on Facebook, Reddit, Google

- Figure out logistics for stocking/shipping

- Cross your fingers and hope that your store somehow beats out the thousands of other stores out there...

It's definitely gotten harder and harder to "win" with a small online store now that Amazon and other web retail sites are so dominant. You might want to consider selling a product directly on Amazon with FBA or another established site like eBay.