I wont recommend any altcoin,so that you can do your own research theres plenty of shitcoins in the market that might be profitable which is why you need it by yourself because if someone has tipped the wrong coin you could lose a lot,which is why it isnt a good idea if you are going to ask a random joe which is which because cryptocurrencies are unpredictable because if the market's volatility.
For me the altcoin to buy is Ethereum even there's a lot of altcoin that have potential but ETH is still the most of them because you can trust to this coin and it is really worth it to have. Also i like this altcoin because it gives me lot of money everytime I'll exchange it, then also i like to buy more of it, until i collect more and then I'll hold some of them then the other I'll going to invest or trade.