An iPhone pro is plenty for a casual/amateur shoot these days. There are even external flashes and strobes that can work with iPhones.
Assuming you aren’t getting paid for it, youdon’t need fancy equipment unless you 1. Need a very specific lens and sensor configuration for a specific style/application. 2. Robust sensor / raw image for super low light noise suppression or heavy post-processing 3. Shoot craptons in a very short period.
Especially for events and candid shoots since more and more people who aren’t professional models haven’t lived around big black cameras and get intimidated by them.