Good advice here already, here's my two cents:
Recoil springs and magazine springs are consumable items (mag bodies as well, actually). If you shoot a lot, you will need replacements. How many replacements depends on how much shooting.
Trigger spring and striker spring will wear out eventually, but aren't exactly consumable in the same sense as the above.
You can get parts breakages anytime, but particularly when your round count really gets up there. And some parts are more prone to getting lost during disassembly. If you're a "belt and suspenders" kind of person, one spare of everything is reasonable.
If you don't want to go that far, after spare springs across the board I'd go for striker assembly (with extra spring cups as well), pins, and slide cover plate.