Eating an organic diet and cutting out processed/industrial food will help enormously with PMS--I know, because after I started an organic diet 6 years ago, most of my PMS symptoms vanished. Then last fall I read the book The Wisdom of Menopause by Dr. Christiane Northrup, MD, which talks about hormones and hormone disruption (it is PACKED FULL of so much useful information for women going through perimenopause that I feel it is a book that every woman should own). I looked at the classic signs of estrogen dominance, progesterone dominance, estrogen insufficiency, and progesterone insufficiency and noted that, due to the clinical symptoms, that I was deficient/low in progesterone. I got some natural/bioidentical progesterone from my naturopath and haven't had any issues with any PMS symptoms since. It's amazing--wish I'd known about this way back when I was 15 and just starting with periods! I would have taken progesterone way back then and avoided having PMS altogether!
I myself (besides the progesterone cream) take Paradise Adaptogens (for adrenal/thyroid health; if they're off, can also affect female hormones), and an immune complex. I used to take Maca root for about a year, year and a half; it helped me. However, I no longer need it, so I don't use it. For some women, red clover or Red Raspberry work well (have used both).
As one poster noted and I will again stress: each herbal remedy works differently in each woman's body. It depends on what hormones are out of whack. For me, finding which ones worked for me involved a lot of reading, researching, and trial and error. One will work now/for a bit and then you might need another one. Or you might get lucky and that one herb is the one that is the "miracle" for you and your body.
I also discovered 6 years ago that I had severe heavy metal toxicity. I naturally chelated through herbal remedies (I used a specific system). After I was done with the whole process (I did it three or four times), I also noticed that my periods/PMS symptoms had vastly improved. When the body is burdened with toxins, it can't clean itself or run properly. When all that gunk is gotten rid of, it really makes a difference in how the body runs and functions.
I've found, though, that eating well (organic, purging processed and fast food) and drinking lots of filtered water has helped me the most. Just giving my body the necessary nutrients it needs via clean living/eating is what it really needs.