First of all don't buy at once to hold coins when the market falls. Analyse whether the descending trend is a bottom. It would be difficult to see it if you don't see schedules of exchanges for the whole year, and then for months as comparison. The prices which you see, will assume a possible condition of coins. From here you learn whether time suits you to buy a coin for carrying out. You can also see the ideas of experts or forecasts of rather current state of a coin