Kit wise the first that jump to mind would be the Tamiya DT-02 range. Granted you'd need to order up a ball racer set for the kit but that's only like £8 and probably a metal gear set.
Apart from them there is not a huge selection of budget kits.. most cheap cars are RTR now or just re-branded Team C
The 3Racing Cactus might be an option, I think you can get them for about £100 or something.
K