When working through sketches and doodles, never underestimade space, espcially the space in between your subject matter. My favorite way to work through a drawing (or doodle) is to make use of that in between space and fill it with colors and pattern.
I like to start with lines drawings.
You could use any type of subject matter, even simple shapes will work!
Then I fill the space with all kinds of different colors and pattern (I love to use dots).
The color and the pattern in the space between the black and white flower drawings create a wonderful push and pull and immediately kicks up those simple line drawings!
Instead of putting your efforts into drawing your subject matter, try challenging yourself to instead focus your time and creativity on the space in between your subject matter.
Use you favorite supplies and colors and fill that space with areas of color, pattern, simple doodles, journaling, texture, etc.
If you use color in your line drawings, try selecting color that is contrasting from the colors that you use to fill the space.
Challenge yourself to fill all of the white space in between your subject matter.