You can do green cartridge motors (360 rpm I think?) direct driven to 4in wheels. this is a little too slow to be highly competitive with (41.8 in/sec, average for vex bots is typically ~60), but is good enough for beginners since it’s ridiculously easy, allowing you to focus on the rest of your robot. Alternatively, I’ve made a list of easy drive gearings that you could use, just know that they’re designed to be used with 6-motor drivetrains.