I trade altcoin on bittrex, poloniex, and c-cex. But all of the time I trade in c-cex it is very user friendly.
I found these are good exchanges for trading altcoins. Each exchange has a big volume altcoin you can trade.
I have an account on those 3 exchanges too. But I use Bittrex and poloniex the most. Those exchanges have a large volume and if you are into altcoins which good volume, because it is more likely they pump it, you need to be there. Remember they also exist for quite some time so it is likely they are here for the long term and will not do a runner, like we have seen with so many other exchanges.