i feel like for you in specific you could work on your colors? use some less saturation in them when you're doing backgrounds and stuff, and there are a lot of common misconceptions about what color some things are that you fall into. Looking up a reference of whatever you're drawing and using that to figure out the colors always helps a lot in my experience. Some general tips for everyone: dont just shade with straight black it hurts my soul, and draw with your whole arm instead of just your wrist, use your shoulder when you're drawing. This makes your lines more fluid and reduces your risk for carpal tunnel or some other wrist injury. you might not be worrying about wrist injuries at your age, but i have mild carpal tunnel already im pretty sure and im not even 18 yet, so take care of your drawing arm!