>>1823322
Investments: The online optimizer tool (link below) told me that Gold Comet filled the most high end kart gaps in my account, and it noticeably helps a lot in this tour. So I took Gold Comet from Lv1 to Lv8/2c.
https://coverageoptimizer.pythonanywhere.com
According to the optimizer, I need a minimum of 36 high end Lv8 karts to cover all 425 loop tracks. Now I have 29. The remaining 7 gaps have some flexibility in which karts I choose, although Gold Driver seems to come up often, along with a few karts that I already have at Lv7 (esp. Black Sneeker and Firefly).
Baby Rosalina Detective is a personal favorite, plus she covers a gap on Tokyo 1T in this tour. So I promoted her from Lv4 to Lv8/2c. She is very unique and fun to use in multiplayer.