Ooh! I dunno if it's better to talk about this in my Artschool post or this final's post, but the "leveling up" portion for me comes a lot from seeing how others edit drawings, and seeing how others edit my paintings.
I am quite the visual learner, and ideas don't really make sense until I see it put into practice. I think Art school is fantastic in that you have a community of like-minded people set on getting better and doing paint overs, helping each other out. Everyone has their strengths and their weaknesses, and when you ask for help, you build a collective knowledge based on the feedback that people give you. It's super useful to retain these things, and ask questions 
Another thing that I recommend is picking art that you like and figuring out why you like it. Is it the colors? The lighting? The story? And then try to understand what they did that made you like it so much. Experiment with that in your own pieces.
IE: My most recent card (Epic Quest), I took reference from a sunny day scene I found on Artstation. I don't usually draw sunny day scenes, I am much more of a moody lighting person, so I took their color palette and tried to figure out what they did. Warm lights, cold shadows, hue darkness towards cools, and sunlights towards warms of any color. Grass in that image is rarely green - it's cold green / warm blue (hue towards cyan) in the shadows and cold yellow / warm green (hue towards yellow) in the sunlight. Independently these colors don't work, but collectively it reads as "green" grass.
It's hard to summarize everything I have learned throughout these classes (it's my 2 year anniversary), but if you have any questions about anything, feel free to ask. I usually go through this process of discovery for every drawing I do.
^This is my journey page, and I have answered a few questions that might be helpful there as well. If you need paint overs or stuff, you can ping me on the discord server, and I'll try to if I have time ^^
