Buying a coin because it is cheap is not a wise thing to do, the reason being that you might not know what the lowest price could be. It is possible you buy and the price continues to fall. So instead of buying with the price in consideration, buy the value. A coin with value will have good products. A product that is needed by investors and those who would like to use it. Although, you might be fortunate to buy it at low price, which then increases your chances of having more profits.
In technical analysis, it is not quite recommended to buy when the price goes down in a moment, you should wait further because it might still fall and it is like catching a knife going down. The best thing to do is like what you've said, to see the lowest dip.