There is no way for you to know your ‘sweet spot’ except by experimentation.
It takes a little time, and rushing is counter-productive.
Here is a thread that explains it:
I have found that two sprays of Instant Sexiness gives me a great edge without being overbearing. If I want the ‘wow’ factor I use three sprays. I am in my 30’s and use more now that I did when younger.