If you want to buy altcoin then Ethereum for sure, i think even if now not growing then in a bull run definetely i think will grow and can give a very good profit, but always people should invest only extra money they don't need.
ethereum is definitely the main choice in altcoin investment, but when looking at the market there will probably be many altcoins that have good markets like BNB and EOS. and we can also buy it.