No pat answer. Depends on your local club. It depends on the number of stages that they run, and the amount of time it takes is really dependant on how many shooters there are, and how tight a ship your local club runs.
Ammo? Beats me. Once again, it all depends. Usually the match announcement will say something about what the minimum round count is. Bring at least half again that amount. I usually try to take double. It sucks to run out.