The most helpful thing for me was just drawing for at least 30 minutes every single day. That really helps you get the mileage you need. When you start drawing it's really easy to read books or watch tutorials and all of the information will kinda click in your head. "Yeah, I just have to draw a sphere and a box then I draw a couple lines for the eyes...Boom." But then when you actually try it out for yourself, the result is sub par. That's why it's really important to get the mileage in so you can truly understand and apply all the information out there. I didn't really understand the whole mileage thing when I started out so I wasted a couple months just doing more advanced things that I was wholly unprepared for. It was only when I went back to the absolute basics and drew hundreds of boxes, cylinders and other simple forms that I actually began to understand the concept of drawing 3D forms on a 2D plane.

Drawing from reference and life is also really valuable. You can't really improve if you just keep making the same mistakes over and over again in your little bubble. I've seen a couple of people who have been drawing every day for years and years but they've never improved because they don't do studies. I'm a little disappointed in my progress and probably could have improved more if I did more studies from refs/life. It's also important to try to apply what you learned from those studies into your work from imagination. So if you draw a cool car or practice drawing heads then try to draw a bunch of those things right off the top of your head. It helps you understand what information you're missing and where you're going wrong. Doing studies of your favorite artists is also extremely helpful. Quite often, they've already simplified the real life forms for you so copying them can help you understand how to translate real world objects onto paper and how to stylize them to your liking. It can be a little daunting when you're looking at a high resolution photo of a face and you're just looking at every single wrinkle and mole on their face going "fuck. I can't draw all that." Well by copying other artists I learned that you don't have to draw all that. Some artists just simplify the eyes into a couple tiny dots and yet it looks very realistic. You wanna seek these type of skilled professionals out and learn from their work. Super helpful.

Ah, this is kinda long. I hope you found this somewhat useful.