Well you should study crypto currency each blockchain in that you can consider a coin will be to the moon, and I think that you should not only focus on one or two coin for long term investment, I suggest ethereum, xrp this next coin after bitcoin has the capability to make it's value more higher in just a matter of time, but all in all you should do it wisely and firmly.
I agree. Sticking to one crypto currency is risky. You need to have back ups. Educating your self with these different type of crypto currencies is a must if you really want to earn money. Each coin has potential to grow.