1. Frequency 2. Harmonics 3. Oscillators/Waveforms 4. Envelopes 5. Filters
The only problem with the last part of your request is that even if you are to watch people design sounds for a couple of hours you might find that when you try to replicate that somewhere else it doesn't sound right. This is partially because every synth/softsynth is different and will produce different sounds and have different parameters. It can be infuriating to get a tutorial on how to produce that perfect "Bladerunner Blues" synth and come out with something that sounds totally flat and bad.
To make matters worse, there are apparently 0 good tutorials on the subject - I just googled for 15 minutes to no avail. The two below cover some of it but I personally can't bear listening to the people who make these videos.
https://www.youtube.com/watch?v=TvQVQuV-Kys https://www.youtube.com/watch?v=lJVlWdzoZ0w