This is a simple fidget spinner that uses a pre-existing ball bearing.

This was my first design on Onshape.  (Although there was an option to make the 3 outer rings large enough to fit additional ball bearing units, I chose not to.)  This is the video tutorial I followed, but then I made my own executive decisions for the fillets.

If you'd like hubs to make it easier to hold the center of the fidget spinner while it spins, then you'll need to also print out the hubs, which I've also uploaded.  While hypothetically it's possible to use the fidget spinner without hubs, it does help the spinning motion to last longer by reducing the likelihood of not accidentally touching the fidget spinner as it spins.

The print came out well, both on the MakerBot Replicator+ (with some modified settings that I didn't record) in purple PLA filament and the Markforged Onyx Pro (solid fill, the rest with default settings) in red PPLA filament.