It has been many years since I last extensively used Garageband. I used to use it to make videos, and sound effects and foley were very useful. But, that was 15 years ago. Does anyone know where those effects went? I have some in Final Cut Pro. Should I use those?
I just remembered... Can't you go to the Garageband menu and choose "Download more sounds" or something like that? I'm not at my Mac at the moment, so I can't look, but I think it's there.
I used to use Apple's "Soundtrack Pro" software for sound effects. That was a very good piece of software (which Apple eventually abandoned), but not really made for musicians. I think it basically became redundant because Final Cut Pro has it's own sound editing functions. If I were you, I'd use FCP.