do not put all eggs in the same basket.
if all "basket" are bad and you are limited and have only one option, it's better to put everything there or put a % of what you have there
there is no reason to diversificate too much, it's very hard to follow multiple investment, and there is the risk to lose more
Yes, it can be a costly error to spread risk only for the purpose of spreading risk. You need to be convinced that these are safe investments. Otherwise it is asking for getting scammed. Unfortunately i tried to spread risk too and what should i say... even though i would have sworn on at least one project everyone of them turned out to be bad apples. Diversification does not help much only for that reason.
At the end if you have slight doubts then DON'T invest at all. It is way better to have 100% coins than the promise to have 200% coins in a years timeframe. Because when you invest you have 0% instantly and the big question is if you will get your 100% bitcoins back at all.