You can look to locals at the track for used gear to save money but if you are not sure what you are looking at can easily pay more than needed.
I think when starting out it is important to save where you can running 13.5 and 17.5 the just stock will be good, you can also look at other esc's that will not break the bank and are still good such as toro, hobbyking and a few others. if you can find a reasonably priced one at the local hobby shop great if not go to online and find one you should not need to pay more than 50 for an esc and in the 50 range for a motor you can upgrade these as needed later.
for servo I say hard to go wrong with the savox there are more expensive and cheaper but it is a good decent servo I use a 1258tg on all my cars and trucks.
radio -- this is the area you want to spend the money once I have an mt4 and like it better than the m12's and the futaba's the only radio I would consider beyond that is a graupner I tried one after owning my mt4 and honestly I kinda like it better and receivers are cheaper when you want to add cars. My suggestion go to the track and ask a couple guys if you can just hold the radio in your hand and simulate a quick drive to get the feel in your hand when you are holding the right one you will now it just stick with airtronics, futaba, or the graupner.
batteries and charger, start out with cheap batteries and before you buy an expensive one try it lol. I started with turnigy from hobbyking and still have them they are good batteries and when my fastest lap is the first three laps of the race I will start worrying more about big battery money lol. charger find one that charges in the 8 amp minimum range the more amperage the better there are entire threads on all these items but chargers are the worst I think there are just so many options it is hard to nail it down I have a hyperion and a hobbyking charger and I honestly prefer the hobbyking cheapo charger and it does a great job and wqas about 40 bucks as an a/c d/c charger hard to beat. but look around at chargers as to the style and rate and amount you want to spend.