Vitamin B5 (pantothenic acid), 1000-3000mg daily.
Try this after making sure your hygiene/skincare is fine but before trying expensive prescriptions with side effects. It's worked for everyone I know, and for people with bad acne it's notable that when they stop taking it the acne comes back. When they start again, it goes away.
Work your way up from lower dosage to higher dosage. When your face clears, work your way back down to the lowest dosage that keeps acne away (I personally now only take it when I feel subdermal breakout bumps starting, but my relative needs to take about 500mg/day). There aren't any side effect concerns at any of these dosages, just frugality - why spend more than necessary.
I personally believe that this remedy isn't more widely known because pharma companies can't make any money off a non-patented vitamin. When I started taking it, years ago, very few people were aware, but now you can google it.
It's water soluble and excess will get flushed with urine. At higher dosages than this, you might get some loose bowel movements (I didn't, but that's what the docs say). There is no 'harmful upper limit' identified - People have taken 10-15g with no serious side effects, though I don't see why that would be needed.
I realize the OP is no longer around, but wanted to leave this here for anyone who is having issues.