Would probably be useful to have a few wishbones and rear uprights and steering arms handy if the worst does happen.
Tyres are more of a consumable thing, if you're in the 540 class and just starting up, I wouldnt see the need to have any more than just one spare set to keep you going, if your budget is tight.
Hopefully with the speed of a 540, you wont be breaking too much. Just focus on getting round the track first without crashing. It doesnt matter if your lap times are slow- its better to be slow and not breaking anything, rather than a few fast laps and you have broken the car with no spare parts to hand...
hope that helps