It depends how much risk you want to take and how much you want do diversify, but I would recommend keeping an eye on these altcoins:
- Binance Coin $BNB
- Neo $NEO
- Zilliqa $ZIL
- CanYa $CAN
- Eximchain $EXC
- Loki Network $LOKI
- TomoChain $TOMO
- Wysker $WYS

There are also a lot of other coins to watch out for, but these are my current picks at the moment. Some of the coins I mentioned are very undervalued coins which I believe will be giving a great ROI in the future, while some of the other more well-known are great projects which is more low-risk investments in my opinion. Do your own research before investing.