To be honest, I think that we will see the dip in 2019. So I'd recommend you to invest all the time in bitcoin but not a huge amount. Just 10% of your income.
If you think the price is going to fall, the investment should be divided so that you do not regret it even if the price increases. Because, it is equal to 50% of the possiblity that you will regret any decision you make.