Just to put things in perspective... If you were taking electronics at a university you'd be in your 3rd or 4th year before you could design your own microcontroller board. Even then, you'd be relying on the chip manufacturer's datasheets and they don't always tell you everything about why certain components/connections/configurations are recommended. And the chip manufacturer may have accidentally discovered that certain things make the circuit more reliable so they include that in their recommendations.
I'm not saying it takes that much knowledge & education and you could learn faster if you focus on microprocessors & microcontrollers...