Soy is supposed to work as Clomid does.
It is supposed to help those who do not ovulate, or ovulate really late in their cycle (like 50 day cycles for example).
If you ovulate regularly and your cycles are pretty much the same every cycle, there is no need for Soy.
As for you much you take, they say to take double of a clomid dose. Many people start around 80mg-120/day and take more after a couple cycles if it doesnt seem to work at that dose.
You take it for 5 days in a row and you can start on CD 1,2,3,4, or 5. The most common is CD3 to start.
I took it in the morning with my other vitamins, but I dont think it matter when. I beleive some take it before bed.
I am not sure where you are from, but many buy it at walmart in the US. ITs about $6/bottle I beleive.
You have to make sure when you do buy it you check for how much Soy isoflavones are actually in the pill, as some people buy some that has very little, which means they end up taking like 6 pills/day. The ones I had had 50mg of soy isoflavones/pill so I was taking 2/day.