Judging from the year you wrote this post, 2018 should have been at that time many recommended ETH as an altcoin that must be in the portfolio and it's proven now ETH is soaring This is high when compared to the price of ETH in 2018. This is evident that the must-have altcoin in our investment portfolio is ETH.
During that time ETH plunged to less than $100, it would have been the time when an investor who looks forward to making a profit has bought hundreds of ETH. Thats not possible right now even if you have $10K intended for crypto investment. What you could have are some other altcoins that also have the chance to make it like ETH.
There are several of them. Although we couldn't really point out exactly which will eventually get there, all of them I think will have a good price at least. SOL, BNB, AVAX, ADA and MATIC.