I know this isn't super cheap, but if you have access to an extra set of frc control system parts, or want to use the set you have until you need to put them on the competition bot, you can build a mini frc bot. Here is the
CAD LINK to the mini bot we built. Since it uses the full frc control system, programmers are able to learn in the environment that they will be working in.
We built the bot out of this
PLASTIC 1x2 Versaframe Stock which makes it really light, and super easy to carry around by just one person. Instead of using an FRC battery, we found a 12 dollar battery on amazon thats like half the size. The drive motors are just a 775pro on a versaplanetary, with 3in colson wheels. Another benefit of a system like this is that the addition of sensors, manipulators, and other accessories is relatively easy. Currently we built a very simple flywheel shooter, that we mounted on the bot to learn how to program vision