First i would like to remind you for what purpose are you buying altcoins? You might have the intention of achieving more and more profits out of your investment, right?. If i am pointing it absolutely precise, why don't you go for bitcoin? You know bitcoin has changed a lot of minds in past year by its fast and frequent price surge, moving from bitcoin to altcoins at the moment would be big mistake in my sense
Some altcoins for short term and some altcoins for long term so you have to decide how long your investment should be before investing.If your are looking for long term investing like more than a year then ETH,LTC,DASH and XRP will be my suggetion because these are considered as classic coins and maintain its price over the period.
Some people converting their bitcoins into altcoin because they want to cash out their profit from the recent price bump of bitcoin and some people feared of bitcoin crash so they are picking some alternative investment for bitcoin which is supposed to be altcoin investment.
But moving from bitcoins to altcoin looks like a mistake in my opinion because I think the price of bitcoin will increase more in the coming years so they have to hold their BTC to have more profits.