I literally only ever got my spirit gauge level up to white, and only like, once, and I didn't even remember how I did that. I got fed up with forgetting how to use it and finally looked up a guide... while Rajang was blue-skulling, and it died before I could even get enough hits in to raise my spirit level on purpose. Wack.
But hey, at least I can make the Brigade layered set now! Which was my original goal anyway; there's a reason this is my first time clearing an arena quest 1,000 hours into the game, at HR 510, MR 268, and AR 154 🙃