As what I have noticed altcoins are following the movement of Bitcoin. If Bitcoin goes up, altcoins will follow, and if Bitcoin goes down, altcoins will go down as well. Others might think that altcoins have the same characteristics but it's not true. This is because their volatilities are not the same to each other, you may notice in the real time prices of altcoins they have the same trend but if you go to weekly and you zoom out, you will see that they are really don't have the same chart. So it's better to focus on one coin to master it quickly.