Paint. It’s relatively fast and inexpensive and makes a huge difference. A pop of color here and there. Then (you probably already do this, but it’s helped) make sure the kids have chores and then force yourself to let them do them. On your daughter’s room. Does it really bother her? If so get some boxes (maybe the ones from the dining room, and help her sort and organize. If not, then let it go. Maybe it’s her haven even when it drives you nuts. Then one box a day. You can do this!