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 (Strongly recommended)
2.
Bitfinex (Stable, not many coins available)
3.
Bithumb (
ps:security issue happened, consider well)
4.
Upbit (Korea exchanges)
Welcome to other suggestion

*******Additional information************
Recommended by FlamingFingers :
Bittrex - 2 years exp. and No issue ever
I just came across a comment saying that we shouldnt have different exchangers and that everyone should be trading only on one exchanger. Well, thats not going to be possible, everyone is entitled to making their own choice. We cant have only one exchanger, there supposed to be different exchangers and they are not going to be offering same services like the other just like the op stated that Bitfinex doesnt have much coins available, but there will be something good about them, a way that they are beating others. So its left for you to choose what you like.