Since I am not the match director I usually stay out of these questions until I see a smart ass response that does no good helping a newer shooter.
My suggestions are this:
Make sure you know the rules.
Make sure you follow the rules
Make sure your gear is proper for your division
Make sure you have all the gear you need
Make sure you have all the ammo you need and more, re-shoots do occasionally happen (Flyer suggests 300 rounds)
Make sure the power factor of your ammo meets the minimum floor level for your division from your gun.
Have a hat, eye and ear protection, water, spare shirt, and anything else you think you need. Have spare eye and ear protection.
Make sure you have spare mags, speed loaders, moon clips. Magazines do break. Speed loaders break, moon clips get stepped on (Usually by open shooters but that is a different sport)
Holsters have been known to break, I have seen a cheap belt break at a match.
Do not think anyone will supply you with anything. You are better off that way and any water, etc supplied will be a pleasant surprise.
As for how stringent the rules will be applied, the rules are the rules. If you know them and follow them you will be fine. If you make a mistake, you will get the procedural penalty you earned. Take it, learn from it, and try not to make the same mistake twice. Don't get upset with yourself or the SO, just move on.
If you are unsure about your ammo making power factor you have time to find a buddy with a chrono and try it. There is too much variation in factory ammo lately to take a chance of a DQ at a major match because of underpower ammo. To the point, I purchased ammo with a guaranteed 130 Power factor because I do not have time to get to a range to try mine out. I may even just shoot my 357SIG factory ammo and use the Gold Dots indoors for the light show
I am shooting the PM Saturday squad after working my regular job in the AM so don't look at my targets, I don't expect this to be pretty at all.
Underwhere, If you need any gear at all send me an e mail. I have spare stuff I would be glad to let you use.
Regards,
Gary