If you want to hold on for a long time, I suggest you invest in the 20 most capitalized currencies. Among them ADA, EOS, XLM seems to be good coin.
You can add to this list Nabo, Lisk, and Ontology. I am sure that these cryptocurrencies will be much more expensive in future. Additionally, watch this video to make the best choice:
https://www.youtube.com/watch?v=i3ygVN_XG-E