Volume or good liquidity is the most important if you are day trading, but you cannot expect that the same coin will always be volatile.
The market has billions of trading volume now, if you are trading with less than a million a day, you'll never find it hard to find a high volume coin to trade.
I wonder how much ripple was when the op posted this topic, if he had invested or traded ripple then, I am sure that he will be full of regrets by now, while Bitcoin still remain the only coin that one can always guarantee its volatility for trading for the next 5 years, because time is also coming when Bitcoin will really not have any volatility again.