If you get the MR-03 EVO's, you will NEED to adjust their settings with the following USB adapter - 82083 ICS on Kyosho America's website.
Look up StephensRCModeling for ics-usb-adaptor-setup

Get one laptop to install the software on (the process is a bit cumbersome but this website helped a lot), and then you can plug in each MR-03 EVO into it to adjust settings like throttle control, drag break, reverse delay etc.

4100kv is a good beginner speed, great for small tracks that are garage sized. This speed is similar to the stock brushed motor that comes with the MR-03 RTR kits. 8500kv motors are very fast and require longer straights and flow-y curves/corners, so probably not suggested for just getting started. A happy medium is the 5600kv motor speed which allows for faster racing, on small tracks once your group starts to feel comfortable driving and want a bit more excitement in your races. The 5600kv brushless motor is similar in speed to the X-Speed V brushed motor.

If you want to see the progression of your and your friend's driving skills and lap times, a lap timing system is a good addition. Build a pvc pipe bridge over the track, install the sensors there, and transponders on each car and you can start compiling race data and counting laps. Maybe even do a season race for points and top 3 get some small prizes at the end. Easylap or I-Lap are commonly used.

For racing on RCP track, the preferred chassis is the MR-03 or MR-03 EVO. The RTR MR-03's are full car/body/transmitter kits, while the MR-03 EVOs are just the chassis, so wheels, body, receiver, and transmitter are also required. I would stick with the most recent releases for MR-03 bodies, such as the Mercedes AMG GT3, or Audi R8, both at 98mm wheelbase. Both are wide tread in the front, which offer cornering stability. If you feel the autoscale bodies are too beautiful to race and damage, consider getting a spare "beater" or "racer" body, either as a spare autoscale, or as a white body (some will come with wheels). Btw, the wings on the autoscale bodies are mainly for looks. They are likely to get damaged eventually during driving and racing. You can get lexan wings that are actually more functional (and paint them up).

For basic upgrades, you MUST swap out any stock tires from the RTR sets as they provide little grip. Get some softer tires in the rear, and medium/firm for the front. Tire tape is important too. You can also upgrade the T plate, and install different front springs for handling characteristics. Also, the "Kingpin Flip" - look on Youtube - is a good free upgrade to smoothen out the front suspension on a stock MR-03 RTR car. A rear disk damper is also recommended to keep the motor pod planted.

That's really all for first upgrades. Get friends/family together, pick up your favorite bodies/cars, set up the track and start driving and having fun!

P.S. take all the RTRs out of Training Mode, and into Normal Mode. Remember to push the trigger forwards twice to reverse the car.