I am using hitbtc for a long time also use ed and polo sometimes if hitbtc is on maintrnace or alts I want to trade is not listed there. I suggest hitbtc because it is the most ui friendly and don't have lots of limits like minimum trade balance or whatsoever but if looking for cheap transaction fee the go on polo just be patient on slow transaction. I wont recommend yobit, its somehow messy and have listed lots of shitcoins newbie could easily get confused on coins with same name.