Investing little by little is a good way to make an investment in a sense that it helps you to escape losses that would have been inevitable if you invested with all your money at once. With this idea, you buy when price are falling but don't be too happy to buy much.
Investing little by little is a good idea, but it is not diversification of investment. In my opinion, diversification is the investment you invest in many types of coins, investing in many markets, such as stock, gold and silver
In my own opinion, investing little by little is a good strategy because in this way you will not lose all your capital when the market prices are dropping and in that way you can avoid losing your investments by selling your coins at its lowest price.