Including myself, I tried to become the 'Amazon of cryptocurrencies' but it's more difficult than it looks like. The problem I faced included transaction fees which I don't like on client's side, transaction time and inflation/deflation of the cryptocurrency.
There are still many places where you can buy using crypto:
https://cryptoslate.com/cryptos/ecommerce/ << have a go there for a list of sites
I also have a school mate who has a nice project. He allows you to go anywhere in the web (amazon, ebay, etc.) and find a product. Then go to their store and pay in cryptocurrency. Their store is shoplium.io (you may have to wait more for delivery but it's still great!)
If you want a professional platform, you may also consider
https://openbazaar.org/