Learning the very basics of photography: what shutter speed, ISO and aperture do, and how to adjust them for each situation.
It takes literally half an hour to learn this, and of course you won't be taking professional quality photos, but your photos will go from crappy to OK or even good, even if you only have a phone (as long as it has manual mode). You know that time you took a random photo and the light and colors came out better than normal? You can achieve that consistently.
After learning this, I felt dumb for not having spent that half an hour years before.
It takes literally half an hour to learn this, and of course you won't be taking professional quality photos, but your photos will go from crappy to OK or even good, even if you only have a phone (as long as it has manual mode). You know that time you took a random photo and the light and colors came out better than normal? You can achieve that consistently.
After learning this, I felt dumb for not having spent that half an hour years before.