I agree with Addams words, although I would not buy a Pro 4 as they have been discontinued (If you get one cheap enough then they are an excellent car, but some vital parts will start to dry up over time and re-sale will not be very good). The Cyclone however is a fantastic car and HPI/HB are well supported around Aus or O/S so parts and spare will not be a problem.
As Addam mentioned, go to your local track or tracks if you lucky enough to have a few available and talk to the guy's who are racing. You don't have to have the most popular or the latest, you just need to buy wisely and only the things you need as you get better. Obvioulsy I'm going to say that the Top Racing Scythe is the way to go, but there is plenty of cars out there.
As a starter the Cyclone S is a very good car to learn with. It is more than capable in 540 and will perform well in Stock until your driving and experience calls for a more PRO chassis. The beauty is you can then simply buy the Pro Cyclone version and transfer you electronics and off you go.
Second hand is not a bad option either as you tend to get good value for money.
There will more than likely be quite a few TC4, Schumacher Mi2EC and Corally RDX's coming up for sale as these models have new versions coming out soon. There will be some good bargains to be had there.
Cheers
Aaron