how do i ask a celebrity to wear my brand or talk about it, and how much does it normally cost (i know it id different based on celebrity)

Ok thanks

The first thing you have to do is find the best way to contact said celebrity. Next, my advice would be to send some samples of your brand. In a lot of cases that is all the cost. If the celebrity likes your brand they will tell others. If they reach out and ask about compensation then cross that bridge when the time comes.