Let's see if I can try to simplify it:

There's another exchange like Bittrex, called GDAX, that is owned by Coinbase. You can transfer your balance to and from your Coinbase account for no fee straight through GDAX. GDAX charges much lower fees than Coinbase, and lets you convert BTC to either Ether or Litecoin directly, without having to convert it to USD first. So, I'd recommend signing up for GDAX and trading through there. Let me know if there's anything that's unclear!

Edit: It does say it offers institutions and professionals the ability to trade, but you don't necessarily have to be one in order to use it. Your experience with Bittrex should be sufficient :).