I think you are the one who can answer that because it depends on what you believe in and what you are aiming for. If you are not after for a long term investment and you need a money right now or you feel that the altcoin is not good to hold, then it's your call if you would like to sell them all.
But for me, I am not going to sell them all. I will choose what to hold and if I sell a certain coin, I am going to leave 20% of my total holdings.

There are many ICO now, I have many suggestion but it is much better if you will found best ICO by your own research, it is the best because in the future, no one will be blamed if the ICO suggested by other person will not success. Look for ICO that have legit team, the best technology, low hard cap/soft cap. Keep researching.

my plan in 2018 is that I will continue to invest in crypto and I believe in 2018 all coins will go up and will give me profit, so I will keep hold of the coins I have and will sell them when I already get profit according to the target I want