Lots of guessing personally, I looked at Korra's turns [link]
I looked at how everything draped on her and then measured about how long I want it on my body. Once I knew the length I took a normal ruler and took notes of how much that would be. I measured my waist as well so I knew how much I needed it to cover. Lastly, I got double what I needed and measured the actual fabric on myself using pins to hold it in place how I wanted it. It's always better to have more fabric than less. I hope that helps!
Honestly it was a month of preparation, About 2 weeks of thinking of concepts on how to make the different parts and a week of experimenting and buying supplies and then another 2 weeks to actually make the outfit. I could only work on it after work and weekends so total hours probably round up to 4 days of making.