In Hamlet, Shakespeare says, "The apparel oft proclaims the man." Your brand image is the perception of your brand by others. You therefore need to put a lot of work into it. Epictetus, the Greek stoic philosopher, states, "Know first who you are; and then adorn yourself accordingly." If you are building a personal brand, effort must be put into how you look. This will first of all tell people that you believe in taking seriously your image building efforts.
Secondly, you tell them that you believe they are worth making an effort for. They need to see that you know that they're worth impressing. This is a display of respect and people will be much more willing to take you seriously.