More Rocks and trees.

When you doodle or sketch do every thing trees and rocks. Even people, the biggest thing is do it with no fear. Do it even if you are afraid. It's just a study.

That is an important thing to understand. Practice, practice, and practice.

Sketch things you see, things you want to see.  Get pictures of art or go to museums. Draw and mess around.

You will learn more by your mistakes than some of your successes. There is no right or wrong any more in art. I use to think you  had to draw by hand and only by hand, but with the digital and camera and tracings things have changed.

Well keep your brushes wet and your paper crisp.