What is the best diet to avoid acne?

Avoid diet hormones. The connections between diet & acne are controversial. The strongest associations in the scientific literature are with cow's milk - thought to be from hormones. Consider choosing organic (or no hormones used) milk and meat products. (most us meat made with hormones) otherwise, no strong evidence that fatty foods or chocolate influence acne. Bon appetit! and track yourself. Each of us different.
Oil. Avoid consumption of excess fat.