If you are new to crypto trading, and looking for a platform to trade, here are some platforms I use.
Share with all of you

1.
Binance : Most recommended. stable, safe, liquidity, commission fee cheap

2.
Bitfinex : Stable, not many coins available
Here is some Korea Exchanges, selling price relatively higher, recommend to sell them here.3.
Bithumb (ps:security issue happened, consider well) 4.
Upbit : Not much volume as Bithumb but no problems so far
*******Additional information************
5.
Bittrex - Recommended by FlamingFingers : 2 years exp. and No issue ever
Welcome to other suggestion 
if you are new ın crypto or ın tradıng first you need to check simdaq platform, you can find it on my signature, its a trading simulation platform, good for newbies and also good for all kind of traders, before going to real trade its good to test yourself inn sımulatıon