That's a long time I'm out of school.
The truth is you should read books about subjects you're interested in to solve a lack of understanding on one subject, and from there teach yourself anything you want, if you were in my situation.
What I did is taking the highest level course I could find on X subject, and trying to understand from other lower level sources the high level concepts I couldn't understand from intuition by the sole reading of the high level syllabus.
I'm all in favor of studying fine arts, but this isn't quite accurate: advertisers (i.e., brands who run ads) rely on people with arts and humanities training—it's not a coincidence that the smallest unit of advertising is called a "creative"!
While it's true that the individual employees creating ads probably studied the arts in some way or other (not necessarily fine arts; "graphic design" is a major not generally included in that category that would absolutely fit an advertising creator), the people who actually run them probably studied either STEM, or, even more likely, business/management.
