The idea I ended up working with for the costume is off of her 2nd game costume. By looking at Sora's Timeless River bit I think they went with his first one because it was a simpler costume. In light of that, I chose to do her 2nd game costume because it's a simpler and plainer costume.
As for coloring and whatnot, it's pretty much up to you. Just look at the costume and figure out what colors will work the best for your idea. I do like the ide aof the flower. That sounds really cute. I might use that in mine if you don't mind terribly. As for the white arms and legs, for my legs I'm doing white tights and then using a type of cream makeup that dries on the rest of my body.
Oh and for further ideas as for the cut of the costume I looked at the two girl characters in Timeless river. (Yes the cow and the chicken) And I got a few ideas to make it more cartoony-y from them. I hope I helped out a bit. Good luck!
Jewelry Bonney - One Piece 75%
Vriska Serket - Homestuck 75%
Cammy White - Final Fight Streetwise 70%
Blackfire - Teen Titans 20%
Young Walter - Hellsing 20%
Donquixote Doflamingo - One Piece planned