Can you suggest me which one is best Altcoin coin hold for 2018? 
I think you should hold Ethereum, because the price is low now. Last year the price reached more than a thousand dollars. So Im believing that before the end of this year the price will get to a thousand dollars or maybe close to that price range, so you should invest in it now and wait for the increase later.
The next coin I think you should go for now that price is low is Ripple (XRP) the price is very low now, or should I even say extra low? So you need to give it a short you have nothing much to lose. As for bitcoin
Mehn
This one is for sure.