Well it will always stay a risk of course but it can be done if you have some luck and if you stay investing in the bitcoin but not with the full amount at once, I just do not recommend you to do that honestly.
There is of course no safe way, but the option that is the closest to what can be seen as the least risky, is simply buying at certain prices levels and holding your coins for a good while. Look at how long the price wouldn't go above $300 last year. If you bought at that price, which I also have done, then right now you would have doubled your investment.