Technically PCOS is an endocrine issue so a reproductive endocrinologist would be the best. Many doctors will also provide referrals to a specialist nutritionist who knows how to deal with PCOS.

I see a gynecologist and my GP. I was recommended to see an endocrinologist, but I never went because the closest one to me was more than 2 hours away, and for the most part, my GP and gynecologist have it under control. If I ever have more serious issues, then I may go, but I live in a very rural area, and don't have a job or the time that permits going to that endocrinologist all the time. I probably should, but for now, it's under control for me.