Which is the best exchange for Altcoins to Fiat Currency ?
This is quite convenient,
Gdax,
Bittrex and Coinbase all fall into this category
All you have to do is create an account with them; activate 2fa and get going
I don't know about Gdax, but Bittrex require KYC and to be honest its a little bit difficult for our documents to be accepted. Moreover there are no actual "Fiat" in Bittrex, they only have USDT which is not real fiat, though it backed up by USD. I think the best place to exchange is Quoine, you can check it in coinmarket cap for their pair here
https://coinmarketcap.com/exchanges/quoine/ they provide real "Fiat (USD) to Alt" exchange. Then you can transfer it directly to your bank account via wired transfer.