We want to make this really easy for you.  
1) Please avoid cotton clothing;  if it happens to get wet, it will lose all of its heat retention properties, which will be unpleasant for you.
2) You can often rent camping gear at REI stores (just be sure to call ahead to make proper reservations).  
3) Please make sure your water bottles are metal;  we recommend Klean Kanteen.

Here is your checklist for what to bring to the retreat:
___ Two separate 64oz metal water bottles for minimum of 128oz (1 gal) total.
___ Sleeping bag (strictly rated for at *least* 20 degrees).
___ Sleeping pad (Hint:  you can bring two sleeping pads and put them on top of each other for additional comfort.)
___ Small pillow (really nice to have at night!)
___ Camping folding chair (height of regular chair)
___ Flashlight/headlamp + 2 sets of batteries
___ Warm fleece jacket for camp + sleeping
___ Warm fleece pants for camp + sleeping
___ Winter fleece hat (this is nice to have at night).
___ Rain jacket (waterproof, not just water-resistant)
___ Shoes (please bring closed-toe hiking shoes as we will be walking off-trail at times)
___ Pants/shorts
___ Shirts
___ Socks
___ Sunscreen
___ Undergarments
___ Bug repellent (non-toxic/natural)
___ Towel
___ Toothbrush / toothpaste / soap / shampoo (biodegradable only)
___ Medications + personal first aid kit
___ Journal + couple of pens