When it comes to creating successful art, you first need to master the principles of design. The most important is composition. If you didn’t go to art school this is the missing piece you need to understand. Don’t even bother painting until you master composing a scene and using the other elements of design to balance it all out. Practice drawing compositions daily, 10 or more a day. They don’t have to be super detailed just 5-10 minute sketches. If you need guidance there are courses out there you can use to learn this skill. This is the one I recommend, but there are many others that will help you learn to design your art before you even pick up a brush.

P.S. This also applies to photography.

You can find this course by Ian Roberts here: Mastering Composition