Hello fellow manga artist! As a person who is still in development of her own style (but it's getting there), my biggest suggestion is to draw art from many different professional mangaka (if you don't know what that is, I'm disappointed in you) from all sorts of genres. You say that your drawings are more Shonen-like? Try picking up a Shoujo manga and draw some of their characters. I would suggest drawings from Arina Tanemura for a start because her people are always so gorgeous! Shoujo is definitely more intricate than Shonen's sketchy style, especially with their clothes and hair, so you may have to spend extra time working on this. You can also look at artwork from Studio Ghibli. They can be simple like Shonen but also really detailed like Shoujo.
The point is, from every manga and anime you look at, there are always things you can absorb from them. For instance, I learned how to make wrinkles in clothing from Bride of the Water God, Kimi Ni Todoke, and pretty much all work done by Arina Tanemura. I learned how to create smoke and fog from reading stuff by CLAMP. I learned how to draw action scenes from Naruto. Observing other's work is a good way to find what you like to do and what you don't like to do as you create a style of your own.
