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.
There is no definite way to differentiate cheap coin and valuable coins since many useful coins maybe arises from the cheap prices so if your are going to find it in their early stage then investing based on hope is the only way.