your friends are right, but I think to invest in BTC enough 50%, ETH 30% and other altcoin by 20%.
I see lots of potential coins, other than BTC and ETH. so I suggest to divide 20% of BTC invest into altcoin.
we will never know what happens in the future, but by looking at projects that have a good team, it can be used as one reference to predict a good coin, like this HDAC project. a project aimed at transaction innovation with blockchain-based IoT by Hyundai, will make this coin more desirable and useful for everyone and provide more benefits than any other coin.
good luck.