Volumes indicate the liquidity of an asset. The greater the liquidity the easier it is to buy and sell, even when there is turmoil, and the lower the Bid-Offer spread and therefore the cost of trading. You want to avoid assets with tiny liquidity as when the shit hits the fan it will be costly to exit. Bitcoin has world-class liquidity. I run a crypoasset analysis site named Blocklink.info. Here is a screen-grab of the most liquid assets in the world.
Always pay attention to Bitcoin. Most altcoins (every cryptocurrency except Bitcoin) are pegged more closely to Bitcoin than Asian currencies were to the USD during the Asian Financial Crisis. If Bitcoin price pump drastically, altcoins price can go down as people try to exit altcoins to ride the BTC profits; inversely, if Bitcoin prices dump drastically, altcoin prices can go down, too, as people exit altcoins to exchange back into fiat. The best times for altcoin growth appear when Bitcoin shows organic growth or decline, or remains stagnant in price.