For me I still make a bad entry on buying But I have learned some lessons on it. First, do not be tempted when the price goes down, because it may be the start of the dump, observe a little longer to have a good decision.
Sometimes you also have to consider which coin that you want to invest not just because that has cheaper price but because of the potential of the coin to recover in the market. Not all crypto coin able to recover after a big dump because some lose their value and lost the investment.
You are right, we must not rely on how much volume it gives and how much gains he gives, because we must uncover first its potential if this coin can endure to the future. If they have a much more bigger prospects.