Where to start?

So, first of all, I'm trying to draw digital art. Yay! It's far from perfect, but I am still happy about it. I don't have a grafic tablet, or how is that thing even called. So the process is a bit more complicated. First i sketch the image on paper, scan it to my computer and then trace it in Krita and color it.

But now something about the actual picture. It's Rainbowshine with a knife. It was highly inspired by a dream i had about 4 days ago. In fact, the dream was so interesting that i decided to write a fanfic about it. It should take me about a week before i finish it.

P.S. Background ponies need love too! :D