Sewing a Katara Costume
I created a costume without using a pattern. This is akin to driving without a map in a foreign country, or performing a musical after seeing a movie.
It’s always best to have something to go by. Either a pattern or a piece of clothing that you know fits your subject. Since this was unique, I used measurements instead. My original idea was that the dress would be slipped on over her head, but it became clear that 
it would be extremely difficult to do that. So I went to plan “B” and made it a wrap-around dress with two overlapping panels, attaching at the waist with snaps. I finished off the edges with a strip of white fabric.
The panel sides had a simple rolled hem, and at the bottom I appliquéd a white piece ( A simple rectangle in the back, a wave in the front).
The next difficulty was I had made the shoulders too tight. This is a problem I keep running into when improvising or changing patterns- sleeves and pant inseams need to be bigger than basic measurements to ensure motion and comfort. 
If possible, find a pattern for the sleeves, even if it is for a completely different shirt, it will help you see how it is supposed to fit in. I eventually used a sleeve pattern from a dress.
I 3-D printed her necklace (but you can purchase one from crafters). I made her arm-bands using this tutorial. She wore leggings and a tank top underneath, and sandals.
We went to Dragoncon! I had so many costumes I wanted to make, but I’m glad I at least finished this one. My daughter wore it to the Aquarium night and pretended to water-bend. . She was so happy!
Cool! Glad you guys had fun.