where to go next / advice on shading

something thats been in the back of my mind recently when making pieces is "what is the next step?" - where do i want to be going with my art and what do i want to focus and improve on. ive generally always been a casual hobbyist ( though my side job of taking on commissions might become a full time thing in the near future for a bit ) so i havent put as much thought into improvement as i maybe could haha. nowadays my drawing time is a bit more limited and i have been hoping to be more pragmatic about improvement - IE: id like to be practicing more on my weak points when i have the time. 

that being said, ive been having a hard time pinpointing areas to really focus on. i know for sure that shading is something id like to improve on - especially in terms of color use and lighting, so ive been doing my best to think a little more about how lighting would effect my pieces. ive had some success with it but i get the feeling theres a piece to the puzzle im maybe missing. "painting" style pieces or more in depth rendering isn't quite my wheelhouse, i definitely want to keep things more on the toony end, but i still want to be able to effectively capture depth and lighting in different environments.

otherwise, any suggestions on places i could improve or where you would personally start are appreciated. any resources appreciated as well!