[tony_sologubov]

Thanks for the question.

Simply put, we need a mod that will work as follows:

first purchase of the customer
- buy 3 products -- one will be free
- buy 6 products -- two will be free

next purchase of the same customer will trigger 10% discount and the bonus products will remain the same:
- buy 3 products -- one will be free
- buy 6 products -- two will be free

Do I understand you properly?

Should this special offer work for all products in the store or for ones from specific category only?

I am planning to create a video tutorial about creating such special-offer-like mods and this mod is a great example, so I probably take this idea and will make a video guide based on it.