This guide describes the old upgrade route. This can still be used to have a relatively RNG save route, but faster routes in the early with more RNG are possible. Additionally, more skips have been found since this guide was written

The main idea of the 100% routes is that you do Semi-Pro first, to unlock Bulleye and Abyss. Bullseye because he is the overall best racer to do the run with, and Abyss to get it out of the way as early as possible. From there there's different variants you can do

VARIANT 1:

Track order:

1. Semi-Pro Circuit
2. Abyss
3. Galactic Circuit
4. Gauntlet
5. Amateur Circuit
6. Ando Prime Centrum
7. Inferno

Upgrades:

• starts with Ebe, switch to Bullseye after Sunken City
• speed upgrade from junkyard before Scrapper's Run. Block 5 or Block 6
• buy all pit droids before Zugga Challenge
• buy the best cooling upgrade available from the store before Andobi Mountain Run
• reset the game after the "Saving Game" text on the podium cutscene after beating The Boonta Classic to skip the credits
• buy the best cooling and accelleration upgrade available before Gauntlet
• in case you got a Block 5 speed upgrade in the junkyard, buy a Block 6 in the store before Beedo's Wild Ride

VARIANT 2: (beneficial for especially Dreamcast runs to save on loadscreens [see below])

Track order:

1. Semi-Pro Circuit
2. Abyss
3. Amateur Circuit
4. Ando Prime Centrum
5. Galactic Circuit
6. Gauntlet
7. Inferno

Upgrades:

• starts with Ebe, switch to Bullseye after Sunken City
• speed upgrade from junkyard before Scrapper's Run. Block 5 or Block 6
• buy all pit droids before Zugga Challenge
• buy the best cooling upgrade available from the store before Aquilaris Classic
• buy the best cooling and accelleration upgrade available before Ando Prime Centrum
• in case you got a Block 5 speed upgrade in the junkyard, buy a Block 6 in the store before Grabvine Gateway
• reset the game after the "Saving Game" text on the podium cutscene after beating The Boonta Classic to skip the credits

VARIANT 3: (for skip runs)

Track order:

1. Semi-Pro Circuit
2. Amateur Circuit
3. Abyss
4. Ando Prime Centrum
5. Galactic Circuit
6. Gauntlet
7. Inferno

Upgrades:

• starts with Ebe, switch to Bullseye after Sunken City
• speed upgrade from junkyard before Scrapper's Run. Block 5 or Block 6
• buy all pit droids before Zugga Challenge
• buy the best cooling upgrade available from the store before Aquilaris Classic
• buy the best cooling and accelleration upgrade available before Abyss
• switch to Mars Guo for Abyss
• in case you got a Block 5 speed upgrade in the junkyard, buy a Block 6 in the store before Grabvine Gateway
• reset the game after the "Saving Game" text on the podium cutscene after beating The Boonta Classic to skip the credits
• switch to Mars Guo for Gauntlet and Inferno

NOTE FOR DREAMCAST:

The original route (variant 1) is the route I got from Tolarus, and from there I adapted variant 2 to optimize it for Dreamcast.

The reason for that is, in all versions of the game, when you enter a certain planet for the first time in that session of the game running, it plays a rendered cutscene introducing the region. However, since Dreamcast loads are so slow, loading these cutscenes takes about 3 seconds each time. So what you do before starting a run, you enter a track on every planet once, to skip the loading of that cutscene. Since the 100% route involves a game reset, which will make you lose all the pre-loading you have done, you want to do the reset as late as possible in the route, to only have as few races as possible for which the game still loads the intro cutscene.