This pubmed article
pretty much sums up what I would say to people that have cases of acne.
As a precautionary method, diet can significantly reduce the frequency and severity of breakouts. People have less acne when they consume less refined sugars than people that do, combined with hormonal changes during growth (pubterty), causes a perfect storm for breakouts.
For general skin care and treatment, I used to go benzoyl peroxide (5%) and Salicylic Acid (2.5%+), the former for short-term treatment for breakouts and the latter because it's a mild chemical exfoliant. Over time I stopped taking benzoyl peroxide mainly because my eating habits drastically changed over time, which included less refined carbs (I do find that the ocassional weeklong fast-food binge gets me a few breakouts). I do get the occasional breakout now and then, but they aren't as severe as I had them in the past.