Depends on your size - I run a couple of times a week and I am a stickler for no bounce! There is nothing worse than seeing a woman bouncing all over the place when running - all I can think about is the damage she is doing to her breast tissue! (although I'm sure blokes don't think the same )

Anyway - go to Myer or the like and get properly fitted. Berlei & some other manufacturers make bras rated for different exercise so you will need to get the one rated for high intensity workouts. I also wear an exercise crop top over my bra for added support.

Enjoy your running!