There aren't exact rules because people's lives are so different. For example, a soccer mom's wardrobe would differ from an executive. Plus there is personal preference. Do you dress up to go out or are you more of the type to just casually have friends over to hang out? Is your office business casual or do you go to a lot of high-end social events.
My lifestyle is essentially casual. This is how my capsule wardrobe for the next three months looks:
And here are some of the looks from this week:
The idea is to not spend so much time thinking about clothes and to have something that fits your life without a lot of excess. I'll keep you posted on how it goes.