If you look for alt-coins with a very high potential of gaining price…. our advice is AELF and RCN at the moment.
https://coinmarketcap.com/currencies/aelf/
and
https://coinmarketcap.com/currencies/ripio-credit-network/
Both have a healthy Marketkap and not to much coins in the open so there is space to grow.
If you are looking for early get-ins….than this two are your pick.