"I want to learn graphic design, both for my current projects and for my future startup (same reason with the suggestion that "non-technical" person should learn to code)"
Theres really no strong reason that a non-technical person should know how to code. Which means you do have to get back to the question - why do you want to learn graphic design?
If you feel that you want to learn it just so you can do that for your start-up, realize that its not necessary. You can definitely get those things done for reasonable price through sites like 99designs (reasonable even for a start-up budget).
IMHO, the best reason to learn graphic design (like most other skills) is because you WANT to do graphic design. In that scenario, how soon you pick it up will not be a factor, which is the way it should be.
About the startup part, let me elaborate. I hope my experience of learning design, or at least trying to learn design, will help me with my taste and knowledge in design. For now, I cannot actually tell apart "good designs" from "bad designs". For example, sometimes I heard people saying things like "It's terrible they chose font X and color Y ..." but cannot see anything terrible in what they're talking about.
Theres really no strong reason that a non-technical person should know how to code. Which means you do have to get back to the question - why do you want to learn graphic design? If you feel that you want to learn it just so you can do that for your start-up, realize that its not necessary. You can definitely get those things done for reasonable price through sites like 99designs (reasonable even for a start-up budget). IMHO, the best reason to learn graphic design (like most other skills) is because you WANT to do graphic design. In that scenario, how soon you pick it up will not be a factor, which is the way it should be.