A set of Rays for track use will not be expensive.
They are the ideal wheel for your proposed use, strong, light, correct fitment, correct offset, minimum unsprung weight etc.etc.etc.
With respect, if you think that a set of "scabby" Rays for track use are expensive then perhaps track time is not for you mate as other items will rape your wallet
Alex
was thinking the last bit too, RAY's would be a one off (hopefully).
Consumables will eat up the budget (if you have one).
rubber > depends on your driving style and how much you push it, probably not to bad at the start but you will start pushing limits once you get used to track driving
brakes > pads,discs > again on driving style (and if you can keep them a bit cooler so you dont melt them!)
Petrol <<< Mine drinks the juice on track
Track cost < to actually attend
More then likely you'll start modifiying the car to be better suited for track... = ££££
I do think rays and another set of wheels with one for dry conditions and one for wet is the way to go and have another set for daily driving.
RACE spec pads that you can swap before track would be the best I think too and then just put some less agressive pads on for daily use.
Or get a tow bar on the Z and buy another car (smaller) for track use
I'll keep a track on spending for 2012 and post it up. My current pads have survived one track use so far (and tyres, but they wont last on a dry session)
What in your own mind do you think you'll be spending PER track session?
My mind it's (no less then, counting the consumables will last 4 track days)
Tyres: 150£
Brakes: 76£ (pads front+rear lasting)
Brakes: 50£ (ps disc lasting 8 trackdays)
Petrol: 70£
Trackday fee: 150£
Engine Oil change:40£ (every outing)
Diff: 20£ (every 4th)
Gearbox:10£ (every 4th)
Brake fluid: 12.5£(every 4th, sooner if boiled)
Probably missed something, coolant fluid to be replaced every year with some decent stuff to help keep the car cooler. (something like waterwetter, I'm no expert when it comes to cooling)