Resveratrol percentage for effectiveness

Hi! Resveratrol seems to be the other “vit C”/antioxidant one can use topically. I am not having luck finding how much is needed for effectiveness yet. Do you happen to know the % of resveratrol needed to be effective when used topically? This will save me lots of $$ there is a lot of expensive hype in the skincare market! Also, is it more stable than topical Vit C?