Tamiya TA05 if you like belt cars. A great starter kit that can can easily be upgraded as your needs require. Very competitive in stock and 19T class against much more expensive double deck carbon chassis cars. They are also very strong and durable. Suspension parts are also compatiable with other models. The TA05 / 415 / EVO IV or V / TB02 all use the same suspension parts (note there is a "regular" and a "lightweight" suspension) so they will still be available for a few years.
There are plenty of places to get parts and kits via internet if your local LHS does not stock. I am all for supporting the local LHS, but why let them decide what you should get ? Try www.speedtechrc.com
and check out there site. They sell the TA05 for $ 125.00 - 130.00 depending on kit (different bodies). They also have easy links to see all the hop-up parts available for the car. Basic suggestion would be get the aluminum shocks with threaded spring perch (easy to set ride height) and universals to start as noted earlier in this post.
As for upgrading to thier top of the line car, just look at the new 30th anniversary edition TA05 Porsche 934 RSR. Full double deck carbon chassis and shock towers, aluminum bulkheads, etc. But if you want to go that route, you would be better to buy a new kit for $ 450.00 + rather than spend that or more on all the hop-ups to upgrade a base kit.