Before you invest into Crypto you should know that Cryptocurrency is considered high risk because it is a very volatile and highly speculative investment (again, right now) that is based on supply and demand and while high risk investments also generate high returns, it's important to only invest what you can afford to lose. Should your long term retirement savings be in Cryptocurrency? I would not recommend it. Secondly all keep in mind that not all Cryptocurrencies are the same so when buying a Cryptocurrency it is very important to do your reasearch on the Cryptocurrency

Now to answer your question I would suggest
Ethereum
Litecoin
Moenero
Tron
EOS