Ok, with regards to the b vits, all the recommendations I've seen are to take a complex rather than a stand alone (such as B6). This is because they all work best 'hand in hand' as it were - and also, supplementing one can mask a deficency in another (not suggesting you're deficient, but because of their interlinked nature that's what can happen).
As for dose, I'd be inclined to start at 100 (I got mine from holland and barrett; the ac too, actually). If you're one of the very rare people who experience side effects at that dose (usually it would take 250-300 to cause side effects which includes tingling in limbs/hands) you can always reduce (by snapping the tablet in half, presto! you've got B50's!)
Be prepared for flourescent yellow pee! That's a degree of the vits that your body isn't utilising coming straight out in your pee.
Take throughout your whole cycle (no need to wait for a new cycle either, although they do their real 'good' work during the follicular stage). Incidently, high dose b vits have also been shown to help mild depression/boost mood/relieve stress. Again, not making any assumptions, but every little helps!
I stopped taking it at bfp, as I was also taking pregnacare which had everything I needed wrt the pregnancy. The B100 was to help me get there 
The agnus castus. Well, in addition to the 'take it!/don't take it!' debate, there is the twin school of thinking that you 'take only until O/take your whole cycle'.
I can only give you my experience, and you can make your own mind up:
When I took it to concieve DS2 and 3, I took 800mg all cycle long (again, AM), and then stopped at bfp. DS2, I was pregnant the second cycle, DS3 the first.
This time, I was taking the same dose for two cycles. At that point, cycles were still all over the place from the mmc, with woeful 9 day lp. So, I thought, I'll up the dose (to 1200mg (3 capsules)) but the increase made me a little twitchy about whether I should take the whole cycle. I figured I had two months worth of 800mg in my system so it would be ok and make me less twitchy to stop at O. Which I did. And got my bfp at 11dpo.
I don't wanna seem like a pusher - I certainly have nothing to gain from you trying it too! - but if your results give you a cats hope in hell of concieving naturally right now, what will it hurt to try?
Oh! One more thing. I read something in the weeks before my bfp cycle about calcium aiding conception/implantation. I barely eat any dairy AND I'm bf so I should imagine that I was deficient. So I also started taking osteocare from vitabiotic that has calcium, D3, magnesium and other trace elements that can also be useful when ttc. The cheapest/best way i found to purchase them was from sainsburys of all places. One pack is £2.50 (cheaper than anywhere else I found) plus they are 3 for 2.
Wow, don't I ramble on? 
If there's anything else you wanna ask, ask away. I'm apparently in a talkative mood!