Every individual have their own taste in altcoins. For me, I prefer ethereum because it is the best coin until now. Just like other people says ethereum is the best altcoins to buy for 2018 because" it is related to anonymity and untraceable transaction". Ethereum is better fpr long term investment and it gives a huge profit. Eth is still popular and it's value are closely with the bitcoin price.
It depends of you because its nice if you know the price of every altcoin you invest because some of them is very long time to grow up the price some of them its quick to growing up the price so it depends of you what you invest but for me ethereum is the best to invest because its proven of investors is good for invest and theres many investors become rich because of ethereum and ethereum is the queen of altcoin.