You're welcome to use as much as you like -- whatever feels good to you / whatever you find most effective 😊 For example, if you're wearing make up and/or sunscreen, you might need a little more than if you're not.
To be honest, I probably vary the amount I use from time to time without thinking too much about it. Cupped in your palm, maybe the size of a quarter, or a nickle.
Overall, I find it best for people to experiment so they can discover what feels best for them because we're all different with different needs (i.e. our skin type, the climate we live in, the amount we sweat, what other products we use, or don't, etc).
Having said that, I do recommend reading my tips for daily skin care because it offers helpful suggestions on the best time of day to use face wash, and how to fit it into a regular routine for best results 😊 https://justthegoods.net/pages/tips-for-daily-skin-care.
I hope this helps!