in this day the price is so high then it is not the time to buy bitcoin wait for the price to go down like 200$ and then buy 1 btc and wait for the price to go up 
like 400$ then you wil win the double but if you buy it now and the price go down you will lose money
What if the price of bitcoin will not go down at $200 and continue increase do still wait for $200? like 400$ then you wil win the double but if you buy it now and the price go down you will lose money As I Said to my other comment if you want to invest in long term the right time is NOW. I repeat again what ever the price if you are looking term investment BUY bitcoin now and hold it.