I will recemend you to buy only coins with good name in market and avoid shit coins, TRX, XRP, NEO, ETH, LTC, XMR are some projects with Trusted team and comunity in backup. Hope you will consider my advice.
That list will be a good choice for the altcoin that we can buy besides the other altcoins because we have so many altcoins that will be the potential to increase in the next bull run. But we still need to be careful in choosing the coins because we don't know which coins that can improve and we should analyze before we buy.
Ethereum will be the next coins after bitcoin that we can buy, and now, ethereum has good movements, and it already increases. But we still need to patient for more and still analyze the coins so we can get the right coins. I am still watching TRX, XRP, NEO because these coins can also increase like ETH.