If you want to try long term investment, I suggest you to hold bitcoin and ethereum. I see most of experienced investors advise people to buy the coins. And I agree with them, till now, the safest coins for long term investment is bitcoin and ethereum. Nevertheless, you can also consider top altcoins on coinmarketcap for the alternative investment. Stellar, EOS, XRP, and Cardano seem to have good future, you also can try them for your additional investment.