Xantham Gum question. For gluten free cookies, I would like to make with pure flours rather than 1:1. How much xantham gum should I use?

My family is gluten free for health. I would like to also use organic ingredients but the 1:1 GF flours are generally not organic. I have various pure flours like sorghum, brown rice, etc. But that means there's no xantham to act as a binder.

Is there a general rule of thumb on how much xantham to use per x amount of flour, specifically for cookies if that matter at all.