Definitely yes. I do buy cryptos when its price drops sharply because this is the only way that I can afford to buy more and gain more profit not only in trading but also I can make it as an investment.
You can do it when you are almost sure that these cryptocurrencies, which you are going to buy, will gain in the future, and do not die like many shitcoins. Now, you can invest in Eidoo and Cardano.