The great thing about doing it yourself is the freedom of choice. You decide the fabric, the color, the shape and finally all those little details like embroidery that makes the dress personal.
McCall's pattern website has a couple of historic dresses worth buying and trying. Here's the one I like the best:
Butterick also has a couple of good patterns:
The second one:
All of these patterns have medieval elements both in shape, sleeves and neckline. Making your own wedding gown is a big project with the potential to be wonderful. I am going to try sow it together with my mother who's a bit more experienced than me.