Fashions didn't change too dramatically during the Civil War. Hoops were added, and skirts became bigger to accommodate them, but they still looked similar to before.
In the course of the day, a lady might change her dress maybe two or three times. It really depended on the day.
In the morning, right after she woke up, she would probably change into what they called wash dresses. These were cotton dresses that they could work in that could get dirty and still be washed often. Because dresses in general took a long time to make (almost the whole thing was hand-sewn) no extra embellishments were added. I'll go more into detail on those in a different post.
In the afternoon, after lunch, they would probably change into a nice wool or silk dress. Wool dress were the most popular because it was so popular; you would just have to be very careful not to get it dirty. Wool is pretty hard to wash without it felting! Trim was added to these, because this was a nicer dress that you would want to be seen in. Kind of like how you probably have nicer shirts in your closet, and then your not-so-nice ones that you might only wear when you're at home
A wool one
A silk one
And finally, if you were the wife or daughter of a rich man, then you might change into an evening gown. They were pretty much always silk, and looked very much like a ball gown, but they might be but a little less low and might have long sleeves. Often silk afternoon dresses were used as an evening dress, with two different bodices that could be worn with the same skirt.
Love how this one doubles as an afternoon dress!
And finally the ball gowns. From what I have been told, the silk for the ball gowns didn't cost very much. Since it would be their nicest dress, they chose to use as much fabric on one dress as possible, going over the top with trims, ruffles, bows, ribbons, and all kinds of other poufiness.
This all may seem like a lot of dresses in one day, but you have to think about the day. Ball's were not every day, and most people where not rich enough attend enough dinners were evening dresses would be required.