Each time people ask this question but they make the final choice themselves. I guess that it is really not possible to foresee the best altcoins to invest in. However, Ethereum is always one of the best choices.
ethereum is becoming a trend in altcoin for now being used as the best purchase, but I see there are several other coins that still have the potential to grow namely litecoin and neo are examples of coins that might be used as alternatives for purchases other than ethereum.