I think and make suggestions to you :
To exchange trade and make a profit, the first thing I think of is poloniex then bittrex. Two sites that I like, with Polo you can Margin, Bittrex it convenient to buy and sell.
Looks like our minds work in the same way when it comes to exchange sites! I also suggest poloneix as it is among the best crypto currency exchanges. Bittrex is the second option but Coinbase and Kraken can also be given a thought. Poloneix daily bitcoin volume is somewhere around 45 million dollars so you can rely on it.