Clothes can sometimes tell us a lot about the person who wears them, but the signals can be confusing if you are not really familiar with the culture of the person wearing them.
Some clothing choices tell us fairly obvious things about a person. Where I live, if you see a woman wearing a head covering, it tells you she is probably a Hutterite. In cases like this, clothing can tell us something about the group to which the person belongs.
Sometimes, clothing can tell us something about the attitudes of the person involved. For example, a high school student wearing all black clothing may well be a "Goth." Such a person may be into the supernatural and things like that.
However, it is not always easy to tell what a person is like from their clothing. For example, you might think a person wearing worn out clothing is poor. However, in some places, this kind of clothing (even with holes in it) is considered to be fashionable. This means that it is sometimes dangerous to assume things about people from their manner of dress.