I have recently returned to my high school days in which I spent entire semesters editing yearbook photos as an extracurricular activity. Rather than purchasing Photoshop however, I found an app (quick plug here, check out Enlight) with a good pricing model that has as many Photoshop features as I think will fit on a smartphone.
I have been editing a ton of photos using this app lately, mostly in subtle ways for my study abroad Instagram (removing people or obstructions, adjusting contrast, directing focus, picking specific colors to be more vivid, etc). Some have gotten more boldly artistic however, and I can see plenty of future applications. For example, I took this picture at the Castillo Chapultepec in Mexico City.
Using only the app and maybe an hour, I then created this piece that I intend to use as the cover image (without the watermark indicating that this is my original creation and not to be copied, altered, or used without my permission) for my study abroad journal when I make it into a more publishable piece about cultural acceptance and exploration.