It may not be a wise decision to buy right now if you believe the price will go off soon before 2018 ends. I mean it is a great idea to buy right now since the price is very low and certainly dipped but you should do this by knowing that you will never know when the price will go up, maybe it will go up before 2019 or maybe it will go up in may of 2019 or maybe it will go up in 2020 and spend all of 2018 and 2019 low. Buy if you can hold it for long enough to wait, if you can't wait and the bitcoin needs to increase before 2018 ends than do not bet your money into it.

I never recommend to go for any other coin except bitcoins even some of altcoins have performed in the past. Keep your investments within bitcoin and you will never get disappointed. Yes, altcoin investments are very much similar to gambling and the chances for your success is only less than 50%.