The thing in the picture really has no defined era. It's got some pre-1800 influences (definitely not 1860s style shirt, they were more tailored by that point and the whole outfit is just too "fantastic"), and what looks like modern women's wear.
The picture will be easier to make a reality than a uniform. A real dress uniform, no matter from what faction is going to take a good 40 hours of skilled labour to make right. A facsimile can cut corners, but you get what you put in. Also, since a certain uniform has real-life defined parameters, you'll come off looking worse if you only do a so-so job because people know what it's supposed to look like and people do make great replicas. You have more freedom interpreting a drawing of something that never existed.
Look for similar patterns to alter if you are not confident drafting your own.