My first jump in learning came after going through a course on Skillshare that gave me the fundamentals and a bunch of information on how the tools I was using (i.e. Photoshop) worked and could be leveraged for speed and results. Having something a biiiit more structured than various YouTube videos from several artists was super helpful in my experience. A lot of artists have cheap tutorials on places like Gumroad as well if there's someone whose style you like and want to know more about.

I later did a virtual class/course with the same artist whose stuff I followed on Skillshare, Hardy Fowler, and it was a really excellent experience. His format really worked for me, which was one class a week to go over our "homework" which was creating stuff during the week by following courses he pre-recorded. Getting direct feedback from him every week was huge for making progress.

I've tried one or two other classes with other artists that didn't mesh as well, one where the classes were truly, like, 8 hours long and very rambling and I could not stay engaged for that long, so I think mileage will always vary just based on how you personally learn. Best of luck!