When I was first considering leaving full-time music teaching to go into illustration, I set myself a challenge of painting 10 digital landscapes over two weeks. I was dreadful at backgrounds, so I figured that if I could a) have the work ethic to get through it, and b) see some improvement over those two weeks, I'd feel a lot better about my chances of getting my art to a level where I could make a living with it.
I used photo reference for each one - just things I found on Google or Pinterest. I started out with simple things, like cloudy landscapes, or undulating grassy fields, before moving on to more complex settings such as gardens and forests.
After about four pieces, my ability at drawing scenery had just transformed. It was such a nice feeling, unlocking a new skill like that! I'd definitely recommend it.