Well this is one of the first times I've used this crystalline-esque styles.
It's kind of hard to explain,but back when i was drawing in animu style I used a weird triangular method of cel shading and basically I used all the knowledge i obtained from my previous drawings onto this one.I think I just developed a habit of adding random excess triangles in some of my artworks just to give it a sharper and overall appealing look.
For this drawing I kinda just plopped triangles at random places and mashed some colours up like putting one triangle of a lighter shade in one of the darker shades.It's really hard to explain but I guess you could just experiment and you'll eventually be able to tell where you can place the shades and triangles overtime. Sorry if this wasn't of any help to you :\