Here's the Banana Cup in 150cc. I Frappe Snowland is somewhat harder with the Standard Mario vehicle due to the lower traction. The game's item usage shows its true colors with two Blue Shells nearly back to back on that track, which could have easily lowered my ranking. Baby Park is the easiest course once you have a set amount of miniturbos per lap. Having triple shells protecting you doesn't hurt either.

Tracks:

SNES Donut Plains 1
N64 Frappe Snowland
GBA Bowser Castle 2
GCN Baby Park (reappears in Mario Kart 8)