Since you are a starting out from zero a sumo robot would be a good choice. It is a well known quantity at this point with lots of parts, simple rules, and very

Since you are a starting out from zero a sumo robot would be a good choice. It is a well known quantity at this point with lots of parts, simple rules, and very focused on the battle aspect. You can build two at once and program them against each other. I’d do a web search for “sumobot arduino” and go from there.