In my opinion the first thing an average computer user should learn is the basics of how a computer works.

I mean, just the basic idea how the hardware and software impact the performance so they can make an informed purchase when buying one.

Than, about the basics of formating, which operative systems exist and why they differ (I am a FOSS advocate).

Than about security, be it malware or privacy issues.

I believe that shortcuts come with experience and they depend on the specific use cases.