Can you see a dermatologist? PCOS is usually treated with birth control pills which you say don't work for you so you'll have to do something different. Spironolactone might be a better choice since it isn't a hormone but instead blocks androgens which in turn helps stop the acne cycle.
For really oily skin try avoiding all processed oils (olive, canola, mayo, butter, fried foods, etc.) and eat whole foods instead (avocado, salmon, whole coconut, olives, etc.). Google "Dr McDougall acne" and his article will come up about cultures that don't get acne and how to eat to clear up skin. It works...along with avoiding dairy and sugary foods.
For really deep cystic acne you will have to do more than diet. It is doing a combination of things that works...not just finding one "magic bullet". The combination approach is diet + something to open pores + something kill acne bacteria + soothing the skin.
I battled deep cystic acne for years and years until finding an approach that consistently keeps me clear (see signature below). Hope this helps!