As mandatory requirements regarding the driver’s and the car’s equipment, the only ones are to wear an approved helmet, which may well be a motorcycle helmet, to wear a seat belt and close the windows when entering the track, to have the vehicle’s tow hook mounted to facilitate a possible rescue and that the brake lights work properly.
Then there are other advisable but not mandatory items, gloves, appropriate footwear and if there is certainly a recommendation on something to improve the car to enter in tandas that any experienced participant would do is to improve the brakes, especially install metal hoses.