There are some people who believe that Bitcoin is the only blockchain based protocol which has value and that all others will fail. These people are known as Bitcoin maximalists and their belief is based on economics, specifically Austrian economics, and that the technology which is great for Bitcoin is not useful for anything else. I am more open minded and believe that there are other applications of the technology which will create sustainable ecosystems but I could be proved wrong here. It is important to spend time doing your own research and building up your own view on where the technology may be used.
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.