Acne help..personal experience would be nice?

So i'm a 15 year old girl, bacne for 2 years, and recently started smoking. I've only had about 8 smokes in 2 months, but I've started to get cystic acne on my chest as well as my back. I'm giving up smoking and all processed foods, sugary foods, dairy, etc. I'm going to do it for 4 months, in hope that the diet change will allow me to wear dresses and stuff and not be concious of being disgusting during summer. I'm just wondering, during summer, will the occassional dairy icecream while I'm out with friends make my skin break out again? I suffer from severe candida.