You should buy other coins, this is not investment advice just saying my personal top pick for 2018 are Steem, REP, Neblio, Aeternity
I dont think so these altcoins have potential of growing much in 2018. It is just not about these altcoins but all other as well, altcoins are not having great market and support in the crypto market. Bitcoin is the coin which is the father of crypto currencies and is the ruler of crypto kingdom.
Crypto coins showed up in market after the invention of bitcoin. Bitcoin is the best ever crypto currency and we all know no other currency is capable of beating it.