Right now is not the good time to buy because bitcoin price could possibly fall around $6000 to $3000 and we all know if that happens altcoins will follow to go down. I suggest that you monitor the market for the upcoming days if we a reversal that is the perfect time to position in the altcoins of your choice.
Why not the best, and why you are only considering bitcoin. Moreover, according to forecasts, he must first fall to 5k, the alts can be very well walked and skimpy. There are inexpensive coins, which are now almost at the bottom, and in the future will give significant growth. This is also a risk, but justified.