The basic one is buy low sell high i prefer to start trading because you can even make more through altcoins then just only bitcoin that is why i would say start trading invest in a couple of good altcoins you trust and when the price of bitcoin goes down you will see the price of altcoins going up.
Well looking to buy low and sell high has been an old strategy which doesn't seem to work in recent times or are difficult to predict in recent times because many volatile commodities or altcoins have been difficult to predict these day and many after the go low doesn't seem to rise back again due to ICO scams going all around .
Everyone has his own investment strategy and the most important thing which matters the most in this kind of scenario is the underlying circumstances. As far as my investment strategy is concerned, I start with the small amount of investment in the beginning and then keep on working hard for having good amount of profit. I then invest that amount of profit as my investment for having better profit.