Yeah, obviously. Like you said, you're selling yourself upon first meeting someone. You're supposed to show your character, and if they find those qualities attractive, they'll get to know you more. First impressions are extremely important because of this. If you go into a job interview looking like a total slob, that reflects poorly upon you because it says you possess qualities that likely aren't good for someone working.
But if you present yourself as well dressed, orderly, confident, etc. then that shows that you're prepared and able to perform the job. Naturally this applies to things other than just job interviews, such as simply meeting someone that could become a friend in the future if they like how you've sold yourself. First impressions aren't intended to let someone know the entirety of your character. It's just a preview of yourself.
“Mutual caring relationships require kindness and patience, tolerance, optimism, joy in the other's achievements, confidence in oneself, and the ability to give without undue thought of gain.”