Courtesy of CADucator/Learn Everything About Design, these videos work as a great fast foundation for getting into Plasticity.
See the rest of their channel with a lot of additional and parallel CAD content:
https://www.youtube.com/watch?v=HQSlC2PXYzE
https://www.youtube.com/watch?v=32av0fy2l7Y
Additional videos going over core principles from the developer Nick.