I'd go for safety stuff first, providing the car is in good condition mechanically.. Helmets you can pick up from motorbike stores for about £40, hand-held fire extinguishers for around £20.. Bucket seat, even if it's just a cheap one like a Cobra or Corbeau Clubman (sub-£100), and harnesses.. ive heard 5 points or better as with 4 points, in an impact you can slide up or down the seat easier.. If you're only planning on doing occasional track days then you're right in considering a second set of wheels / tyres.. Obviously slicks or cut-slicks will wear down quicker but they're definately worthwhile on the track and it's better than trashing your daily wheels and tyres....