I am partial to that classic watercolor subject, fruit hanging on a tree. I have many photos of a persimmon tree at the end of my street that I hope to get around to painting one day.
I signed up for an online course with Birgit O'Connor called Shadows and Backgrounds because I love one of the paintings she does in the course, a branch of quince. I signed up for, and actually completed two of the projects for, another of her classes, and I learned a lot--about planning, about going big ... (And the classes are a good deal, imho: when you buy, you have access forever! Birgit supplies all the info and references you need; there are FB groups to interact with other students; and the videos are very good.) But I still have more to learn from her.
For example, for some dumb reason, I don't know why, I started this painting before watching Birgit's video. Luckily she has a video on correcting blooms--I don't usually mind blooms, but the one on the big leaf is just distracting.
Now the plan is to finish this, then do another a la Birgit.