An update!
I finally finished my first pass at this costume. The iteration in my last photos was lacking a few things. For reference, here's my original vision:
The version I wore to this first con was missing tabards, which eventually I did make. Here was the "all the right parts, but still WIP" version of the costume.
I hadn't made an inner tunic yet, so I was actually using a this thin sweater my wife had. The obi is just a long strip of scrap left over from the robe with the edges tucked out of sight, and the tabards are single layers of fabric(not quite the same length) with the inner edge hemmed and the outer edge bare. They got the job done.
And here's after properly finishing the costume. Well, "properly." I still have a bunch of hemming to do (I hate hemming).
Ironically, the part that turned out the best is the one that's least visible; the inner tunic.
I'm pretty happy with it, but there's definitely more to do. My robe has a number of weak seams and some outrageously uneven hems, and I'd kind of like it to meet Rebel Legion standards, so it needs to be a bit longer. I'll probably remake it at some point. My outer tunic is somewhat patchy from use of a bad pattern, and it was just one layer of cotton gauze. I've already started cutting pieces to remake it more accurately and with a lining. Probably need a slightly wider obi, too. Once that's done, I'll feel comfortable moving on to the next Trials costume, Wayward Borom.