Ok I will be serious. That would depend on what they are providing like meals and lodging. Obviously clothes that you can layer in case the weather changes. Plenty of feed for your horse, you own buckets, slicker, I could go on forever but really need more details on what the camp provides.
Definitely depends on what they'll be providing. Will they have food and access to water for him/her? As for other stuff you need to bring. Think of it kinda like a show checklist. Buckets, blankets, tack, grooming equipment, vitamins, etc. really you need to bring the things you use on a daily basis with your horse.