What type of music will you be recording? You want to make sure your mic can handle the volume. Where do you plan to be in venue? You trying to stack tape (record from PA) or set up in "sweet spot" in the audience, or open tape near the SBD?
Starter mics for a lot of people have been CA-11 or CA-14s. You will need a battery box or an amp to handle high SPL music though.