If it's your first event EVER, leave it at OEM pressure (what's listed on the door jam) and check after each run session and make sure it's not over 40 psi HOT right after the run session.
There's nothing you can do to "keep from destroying the tires" without increasing negative camber, or learning how to manage your tires and contact patch, which, at your first event, you'll definitely not know how to do.
Lastly, if you have some chalk available to you, you can try and mark the sidewalls to make sure the tires aren't rolling over too much. But if you can't get enough camber in the first place, it's not going to really make that big of a difference. Try and keep the tire pressure in a range where the wear marks come near the edge of the "Bibs" on the sidewall (usually a little Michelin man denoting where the tire wear bars are). If you're up at 40+ psi and it's still completely wiping out the Bibs on the tires, then you're simply pushing way too much slip angle for your own good at this point.
If you've got hundreds of events under your belt, and this is your first event with the M3...You'll know what you need to do within 3 laps. Good luck.
EDIT: If it's not clear to you now, it is IRRELEVANT what your cold pressure is. It's your HOT pressure you need to keep an eye on.
The hell I don't! LISTEN, KID! I've been hearing that crap ever since I was at UCLA. I'm out there busting my buns every night! Tell your old man to drag Walton and Lanier up and down the court for 48 minutes!