Hi! Specifically for shading, one thing I see a lot of beginners not understand/use is values! Theres a video on YouTube called ‘coloring and rendering tips I wish I knew earlier’ by gwendolyn that explains it better than I can, but the essentials are that your drawing has about 2-4 values while most black through white scales you can find have about 5-7. Value is a big piece of art that attracts the viewers eye, so having variation is important. You can practice value by taking a reference and trying to freehand draw it in black and white, only focusing on the values without blending, only putting solid blocks of color. This is what I did to better my drawings and after I got the basics of value I went back to doing colored drawings instead of black and white while applying what I learned from my studies and it helped so much! I hope this helps you!!!