As a reasonably clever but not exceptionally bright dude myself, I’d say: start with the donut.
https://youtube.com/playlist?list=PLjEaoINr3zgEPv5y--4MKpciLaoQYZB1Z&si=0TVnvFIyaN8MISMC
It’s a classic blender tutorial that has been kept up to date with Blender’s latest release, and will help you become familiar with most of Blender’s major features.
After finishing that last month I’ve been making lightsabers, mountains, cities and bridges. Happy Blending!
It’s also been great to see new affordable entry-level equipment become available. I had a friend finally get an espresso machine a few months ago, and I was able to point him to the Fellow Opus, which is only $195 ( and was on sale for $150).
To your point on “When to invest?” - there are certainly things this grinder could do better, but he has yet to hit a real problem in his coffee making. So sure, an $800 grinder might have fewer fines or more micro-adjustments, but that’s not really offering any value to him at the moment.