That's why I used to trade mostly Ethereum, because it was more predictable... Now I mostly trade Dogecoin, because people dump it like no tomorrow to buy random altcoins, so it's very easy to get big profits just by putting the coins back on other side of the trade book... Another one of my favourites in LTC-ETH pair, because the difference between buy and sell sides can be quite large on some smaller exchanges... In the end I withdraw everything as LTC, because Dogecoin withdrawals are manually processed on some smaller exchanges even though other coins are automatically processed.