This garment needs to breath and absorb perspiration. They are available new from many sources or you could look for one at the thrift store. This is a very easy garment to sew from scratch, as it is loose and unfitted. Modern patterns that simulate this style as sundresses or nightgowns are available, and can be used by adapting the neckline to be wider. When you are ready to acquire undergarments, this will be the most essential.
Gowns require a corset to achieve a period correct look.
You will really need it to make a ball gown look nice. The corset takes some getting used to. I personally find them uncomfortable and restricting garments. Some ladies I know with back problems claim the corset feels very good when you get used to it. We simply must endure as our ancestors did and suffer for vanity.