There are a few ways to do this you can either play though career and rack your brain and try and win each individual event or you can go into quick race, set the AI to Exhibition, race type to Combat Race and track to Canyon 1. Then just start it and win. then rinse and repeat 100 times. If you are good this can take 50 seconds per race or if you are a god you can go 36 seconds.
The wins can be stacked across all game modes - Multiplayer and Singleplayer.
I would suggest changing race type every 20 time so you can work towards these as well:
Magnet Mayhem Master
Velocity Master
Combat Race Master
Knockout Master
I would also suggest changing racecraft class every 10 times so you can work towards these as well:
Titan Master
Mercury Master
Aurora Master
Phoenix Master