Rule#1 in investment: 'always try to diversify your holdings'.....So the answer is Yes! Don't only put all your investment in BTC....Try to diversify as much as you can.
But definitely, do your own due diligence exercise in full before jumping in and investing in any alt Coins.
I agree. Diversify is what the one have to do. It will reduce the risks, also might bring strong benefits in the future. Let it be casual ETH or BTC, let it be some alts as XRP, Monero, MGO, TRX or any other you like the truth is that it's better option to hold different currencies imo