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
+1 everything becomes expensive when tracking and from experience never mix tyres in track as in the wet the car will handle like crap.
Driving with a set of wheels in the car is silly. You can't see out the rear window and can't see your passenger side mirror.