I was too terrified that I'd ruin it if I did shading xD I've got some gray scale markers but I tried them out on another drawing and wasn't overly found of them.
I'm looking into the manga studio program which would have shadings and textures that I could add.

I completely agree for the bubbles though, I forgot to leave space for the bubbled and I wanted to be able to move their position if i found the placing annoying later on. I used a cut out tool, and that was the best I could get for a ring.

I should probably put up that gray scale attempt to get advice on how to work with those too...