I started cryptotrading months ago, and I had the chance to test few of the best trading platforms and here is my ratings.

Binance (Excellent)
KuCoin (Excellent)
BitFinex (Excellent)

Poloniex (Satisfactory)
Bittrex (Satisfactory)
Kraken (Satisfactory)

HitBTC (Good)
GDAX (Good)
CEX.io (Good)
BitStamp (Good)

Huobi Pro (Testing)
BitFlyer (Testing)
CoinOne (Testing)
Upbit (Testing)

Bithumb (Not Rated Yet)
OKEx (Not Rated Yet)

Drop the list of your best trading platforms here.