This was the second cosplay I hand-sewn, and it was pretty difficult to figure out!! I modified a long, sleeveless dress pattern so that it went down to a point in the front and in the back. The side panels I made separately, with several layers of interfacing, fabric glued the gold trim around, and then sewed to the dress.
The collar was the hardest part to figure out, omg. What I ended up doing was using craft foam, a lot thicker and stiffer than interfacing, and I had my mom help me pattern around to the shape of the collar I wanted and glued together in that shape. I then sewed the brown fabric on top of the craft foam and the gold trim, and then sewed the extremely stiff collar to the dress afterwards. A weird procedure, but it worked to get that really high, really stiff collar that I needed. For the white stripes down the front, I found some white (with a tiny bit of gold that I liked) string almost, and fabric glued it down the front, being very precise to keep it a straight line.
The arm gloves I made with the same brown fabric, with a thick gold almost plastic-like lining that I glued to the ends. (They don't stay up very well orz), and velcro them to some white gloves I found. The boots are made the same way, and I just wear a pair of white pumps over them. For the boots I ended up gluing some velcroe to my red tights, and some to the inside of the boots, which keep them up.