I have the same problem: thinning hair, and have been on the net, looking into it. Here's what I've learnt, so far...
Low iron, B vitamin deficiencies, dodgy thyroid levels, stress, menopause, heavy dieting and pregnancy can all cause hair loss in women. A blood test can determine whether you need medication.
Generic vitamin pills are the same as the fancy-pants stuff labelled for 'hair, skin and nails', and way cheaper.
There's loads of fancy potions and lotions on the market, but they're mostly rubbish. Castor oil, sulphate-free shampoos, head massage and caffeine shampoos are often suggested, but don't pass muster in clinical trials. Minoxidil is the only clinically proven treatment for hair loss. (Don't get it on your face unless you like having a beard).
The women's version is more expensive as women will pay more for such things: the formulations are exactly the same.
Regaine (for men) is the market leader, and is also marketed as 'Rogaine' for women. Internet tells me that 'Kirkland' make a 5% solution, same stuff, same results, but Kirkland is cheaper.
Ebay is a good place to buy Minoxidil, but be careful that the seller lists the expiry date as some sellers sell out of date stock. If seller does state a 'close' expiry date, then these are often cheaper.
It takes around three months to see results, and most ebay sellers sell 3 month supplies, again which saves you money.
Am glad other people seem to be having results with Minoxidil. I'm hoping it'll work for me, too.