Some basic tips for leveling up and upgrading your characters.
Mario+Rabbids: Kingdom Battle is a strategy RPG- which means, obviously, that you are going to have to level up your characters. And while there isn’t a traditional level system with XP, you still have to invest in character skill trees to unlock more abilities for them.
So, here’s how this works:
There is no way to expedite this process- you can replay challenges to grind Orbs, and you can use those Orbs to level up, but the cost of subsequent abilities increases way too fast for you to be able to keep up with it meaningfully. This means that the best thing for you to do is to play the game naturally, but be thorough and comprehensive, and make choices about what you want each character to be.