If you cannot find some altcoins to invest to, you should do some research and look for some promising coins there. Also, you can just rely on the top ranking of coins in the market place. Check out the Top 20 on the market and do some research about those coin for you to be able to filter those coin that is promising or not.
The potential of the Top 20 should have a large increase in altcoins with low market capitalization. So I choose some premium altcoins as a supplement