This can be taken into consideration to choose an exchange :
1. security
2. trading volume
3. reputation
4. fees
5. other
I can't give any suggestions, I am not active yet on trading , still be hodler. But currently I am using Qryptos, Kucoin, Bigone, Okex, Mercatox, my local exchanger, and others
Waiting for experts advice to tell us more about this