Amateur Circuit:

Ebe Endocott until you unlock Aldar Beedo after Beedo's Wild Ride.

Race 1-3: Ebe Endocott Race 4-7 Aldar Beedo

Note: If you have problems on Vengeance with Beedo you can switch to Clegg Holdfast for that track. If you play on N64, Clegg is also a viable alternative on M100 and Spice Mine Run however he is significantly slower than an (optimally played) Beedo.

Semi-Pro Circuit

Ebe Endocott for Sunken City to unlock Bullseye, from there take Bullseye until you unlock Boles Roor after Zugga Challenge.

Note: Boles Roor is supremely difficult to control but he is the fastest no upgrade pod in the game due to his incredible high base speed. I highly reccommend learning him if you aim for a good time in SPC No upgrades. You can use Bullseye instead of Boles on the last 2 tracks if you do not feel comfortable however be aware that it is a huge timeloss by default

Race 1: Ebe Endocott Race 2-5: Bullseye Navoir Race 6-7: Boles Roor

Galactic Circuit (any%)

Complete Executioner with Ebe Endocott to unlock Toy Dampner. Toy saves time on all remaining tracks and is the fastest option (tied with Mawhonic on the later tracks but significantly easier to use).

Note: This Circuit has by far the hardest tracks so its a valid option to use Ebe on the most difficult ones when you are still learning the category (Grabvine, Fire Mountain, Boonta Classic).

Race 1: Ebe Endocott Race 2-7: Toy Dampner