What equipment do you need to make an assembled car electric motor RC to be ready to race?
Aside from the car or truck body, you need a motor and a speed control.

Radio Systems Motors Battery Packs & Chargers

Speed Controls Parts and Accessories

Those include a 2-channel radio control system with "AA" batteries to power the transmitter—plus field accessories, including NiCd battery packs, charger, and a field bag (basically a tote bag designed to carry your car and equipment when you race).

2-CHANNEL RADIO SYSTEMS for a Car Electric Motor RC
This controls the car, just like the gas pedal of a real car. It consists of a transmitter, a receiver, and servos.

The pistol-grip radio offers the feeling of real driving control with both comfort and convenience.

Turning the wheel of the transmitter duplicates the steering techniques for full-size automobiles and boats. The wheel is located on the right side of the radio and the throttle is controlled by the left index finger in the trigger position. The Futaba 2PL 2 Channel Radio System is a great Starter Pistol Grip Radio System.

a) The transmitter, the unit that you hold in your hands, sends steering and throttle commands to the vehicle.

b) The receiver, mounted on the inside of the remote control car, catches the signal from the transmitter. It then translates your commands into action by sending the signals to the third part of the radio system: the servos.

c) Servos are also mounted inside the remote control cars and are plugged into the receiver. Messages from the receiver tell the servo in which direction it should move and for how far.

The servos for your car electric motor RC move the steering and throttle linkages to control speed and direction, as you command with the transmitter. Electric cars may use a servo and a mechanical speed control for throttle control, or may substitute the assembly for an electronic speed control, better known as an ESC.

Frequency Groups for Car Electric Motor RC Cars: There are two different frequency groups to choose from with car electric motor rc...

a) Surface Use Only (75 megahertz, Channels 61-90): Cars, boats, and other non-flying models must use one of these channels. Radios designed for cars/boats exclusively with a steering wheel or pistol grip control are only available on these channels.

b) All Uses (27 megahertz, Channel Code A1-A6): Although legal for all models, we suggest you use 27 megahertz only for surface models. This is because of the possibility that some unseen operator may innocently be operating a surface model on the same channel within range of your model airplane, causing interference and a possible crash. (Note: countries outside the United States may offer different frequency allocation schemes.)

When you go to race, tell the official in charge of the race what frequency you are operating with because each driver must operate on a different frequency. You will be assigned to the races you can drive in with your frequency.

A RECHARGEABLE BATTERY PACK is required to run virtually all electric cars and trucks. These are typically made of 6 or 7 individual NiCd cells wired together and wrapped in a plastic film. Most drivers keep several packs on hand, using one to race while another is recharging (which usually takes about 20 minutes).

Most car electric motor rc drivers bring a battery charger with them to the race track so that they always have on set of batteries charging.

SPEED CONTROLS for a Car Electric Motor RC
The control system sends the power from the batteries to the motor. This device gives you command over when and how fast your model moves, and whether it runs in forward or reverse.

There are two kinds of speed controls: Mechanical and Electronic. Most models designed for newcomers include mechanical speed controls. They work fine and allow beginners to start without considerable out-of-pocket expense. The disadvantage: they require occasional maintenance—as well as a servo, linkage and resistors for operation, all of which increase your model's weight.