Specifically, some species of Psilocybe look almost identical to some Galerina species, and sometimes they grow right next to each other. You don't want to eat Galerina[1].

In my opinion, hunting shelf fungi is pretty beginner friendly. As far as I'm aware, many species are edible, and those that aren't will just give you a stomach ache instead of giving you liver failure.

[1] https://en.wikipedia.org/wiki/Galerina_marginata#Toxicity