This is a question been asked in Design Validate & Document section. In Fusion 360, if you want to create a Gear, you can
1) To create a spur gear from Add-in dialog as following command: Menu > Scripts and Add-Ins > spurgear
2) You can also insert stardare parts from McMaster: Toolbar > Insert McMaster-Carr Component
here is a quick video
There will be also some Design Accelerator toolsets been planned to be added in Fusion the near future, if you want these toolset, please feel free to post this requirement to our IdeaStation. Our UX and product management teams are frequently reviewing this to determine the priority of our planned features
Regards,
Adele
Fusion 360 Quality Assurance