Personally I'm a bit wary of self-medication, and wouldn't take anything at all that might 'regulate the cycle' without checking with the doctor first. My reason for this is that if your cycles are irregular, there might be an underlying reason - that irregular cycles might be a symptom, not a cause, of an infertility issue. Taking agnus castus might just hide the problem.
Also, agnus castus is contra-indicated for some people, and with some prescription medicines. Side-effects can include: gastrointestinal problems, acne-like rashes, and dizziness.
My view on this, then, is if your periods really are irregular (ie vary by more than a couple of days each month), and you can't put that down to an obvious cause (like recently coming off the BCP), then it's worth checking with your GP. It's quite possible that if you did have a hormonal condition, you would be advised to take agnus castus...
As for vitamins - you should definitely take folic acid. The easiest way to take the vitamins you need is in a pre-conception/pregnancy multi-vitamin supplement, such as Pregnacare, which contains folic acid as well. Your husband should take vit C and zinc, and ideally selenium as well. You can buy combined vit C and zinc tablets - brazil nuts are plentiful in selenium, and 3 nuts a day provides more than enough.