When the market is down the best move is to buy because many traders sell their altcoins in low price because they afraid to loss their money.
I purchase coins when the prices are cheap so I don't lose a bunch of money if the price crashes.
If you perfectly buy it on its dip surely you will be able to gained a lot when pumped will start to show up, still a good strategy buying low and selling high as opportunities will be just around the corner for those who really take this market seriously, it's been proven that people who knows to be patient and continue to sort the market and keep buying dumped coins happen to earn big profits after the bounced back.