I usually Invest a very small amount of bitcoin to another coin because I know this time is very crucial to invest in any new coin or even in an old coin.
Any suggestion from your side which is good for long term
Instead of selling a portion of your bitcoin and reinvest it into few other altcoin why don't you take a loam on top of your bitcoin and invest them to the altcoin. Most of the lending platform take wrap bitcoin as collateral which you can use to borrow stablecoin. You can pay back your stablecoin by making profit in the altcoin and unlock your bitcoin.