It depends on the make up of your group really. You only really need the main rulebook.
I own all the books but most used are Core Rulebook and Run Faster.
If you have magicians then I would say get Street Grimoire and Forbidden arcana to a lesser degree.
If you have technomancers you would want Kill Code. Data trails maybe.
For deckers I’d say Data trails then maybe kill code.
Face then Run & Gun’s armor sector is almost a must.
Riggers would love the mod rules in Rigger 5