it should be noted there is a difference between “ambassadors” and “athletes” butThe most common method I’ve seen is through the use of a discount code. Whenever the ambassadors code is used upon checkout they typically would receive the discount amount.

Ex: customer purchases $100 worth of product and uses ambassadors code (am15) for 15% off total order. The ambassador would receive $15.

Other perks are usually they will be provided a code that they can use for their personal use, as well as early access to new releases and such.

As far as what they’re required to do is more often than not they essentially have to post an add for the brand on their social media platform a specified amount of times. (Per week/per month).

An Ambassador for a fitness brand requires various deliverables to be done.
Your focus should not be on how is he performing and what you're paying to him , but about what is he doing and what do you expect from him.
Your brand name and your brand publicity is associated with the name of the ambassador.

I would love to talk to you about it. You can approach me on Instagram : bing_chandler61200

Would love to help you , not charging you much :)