What I usually wear on my first date is my favorite clothes and I see to it that I also wear a classy perfume. And not to forget, I would take a bath and let the soap linger on my body for 2 minutes. That would result in a pleasant scent when I perspire. So even if you don't apply deodorant, when you have taken a good bath with the lingering soap, you would be okay. That would help you project a good impression. But for the other party, I guess all you need to determine is the same - the clothes he wear, his scent if possible.