One of the best and most funnest (no it’s not a real word, yes I’m using it) practices for art is mark making.
It’s a great warm up skill and you can come up with tons of cool mini-compositions. And another great thing is that you can use them over and over for various ideas for your art—line, texture, darkness, light, anything really. It’s free and it’s very effective tool.
Line, weight, expression, sad, mad, excited, cool, calm, whatever you want to express or convey, you can with a simple line.