I think what Adam means is buy in large quantity rather than bulk roll ... eg. if you go to CP and ask for 10 rolls, you should get better prices than 1 or 2 ... and perhaps better if you ask for 20.
I don't know if you can even buy negative film in bulk rolls ...
One note ... if you're shooting a wedding, don't take a chance, go with a film that you've used before, or buy something and experiment so that you know how the film behaves in different light conditions in your camera (each camera model may have slightly different exposure characteristics, especially if you use the highly professional "P"rogram setting

)
I would also not buy any "off" brand ... stick with the biggies like Fuji, Kodak or even Konica. And do the first process at a "pro" lab, you don't want the chance of a neighbourhood shop stuffing your negatives up unless you've used them consistently.
Weddings are always a worry ... very high expectations, coupled with the fact that you've only got one shot at it.
And since you're shooting negative film, just burn film throughout the day ... don't hold back.