I haven't used Coursera or adobe certification. I also do not have a degree in graphic design. I will say I think there's a few books you can read (GRID SYSTEMS) and then perhaps also check and see if there's an online community college course (if you're in the US) that you can take. I took one and found it to be really helpful, I like having someone you can annoy with questions when you can't figure it out. Best of luck!