Transaction fees with Dogecoin or Ripple for small amounts
Fully understanding where you come from, IHMO you should choose the crypto currency which most of your potential customers keep in their wallets anyway. Especially when it comes to small amounts (as you say) hardly anyone will be willing to go to an exchange first and trade 0.0005 BTC into a different coin only to pay you.

I would suggest to take a look at the Lightning Network (https://en.wikipedia.org/wiki/Lightning_Network).