See the Catalogue of Drive Gearings for pretty much every good gearing. I would also say to use at least four motors on your drive, and to use six if possible. For help with build quality, there are several good resources, such as Designing a Quality Drive and Designing Another Quality Drive.
If those seem a bit too complicated for your team, a good place to start is Creating a Basic Drive. As always, you can use the search bar if you want to find more information.
Good luck with your design this season!