Well, the two best exchanges are Poloniex and Bittrex.  These are the world no 1 and no 2 exchanges which deals in bitcoin / altcoin market.  They contains the best altcoin in the best possible price and i have never had any issues with their support. Poloniex also offers marginal trading and lending option and it is good if you have more money and you can lend only and get interest on that.