Update!
So, this dress I got two years ago had the perfect bodice for Serenity. So I'm going to use that as my base (Why waste fabric?!), and it still fits!
I also have a line of beads I can use for Princess Serenity. (Flower shaped pearls)
Just need to buy the chiffon, organza, wig, and beading. I'm going to go with a mix of white and cream for her dress.
But it may be cheaper than expected, now to look for local fabric where houses.