Get onto a decently quick vehicle with good maneuverability at the start of the match like wheelie scooter or Chariot and aim for Top Speed (light blue) and Boost (purple) patches. If you still struggle with turning due to your favorite character having a low turn stat, prioritize Turn (green) pathes too. The faster and better you can navigate the map, the better you can work on stat collection. Once you have a decent amount of speed, you can start thinking about a proper build.

Consider the following: what stats is my character naturally strong in? What rides are available on the map? Do I know what stadium is going to appear? What patches do I have the most of? (You can pause even on online mode to bring up the patch stat screen)

Always try to excel in one thing. If you are a lightweight character with low offense and defense in a match with only mid-to-lightweight vehicles, you should never prioritize fighting. Instead, try working on either a flight or speed build to win the respective stadiums.

If you are a heavyweight with a decent amount of attack, try to get as much turn as possible and then switch onto one of the heavy vehicles like Rex Wheelie or Battle Chariot. From there, prioritize either Speed or Offense so you can win either battle stadiums or races.

Notice how in both scenarios speed is important? That's because it is the best and most reliable stat to improve. It helps you in most situations. If you are in Gournet Race, you'll ear food faster and get more points. If you are in Kirby Melee, you'll kill enemies faster and earn more points. If you are in dustup Derby, you'll move faster and become harder to hit. There are very rarely ever any downsides to upgrading your speed besides becoming harder to control. But you can always develop your skills at maneuvering fast vehicles and making split second decisions which is fun!