I approach every kit this way...

1) Evaluate my needs;
2) Evaluate my environment;
3) Develop a strategy;
4) Develop a kit to help implement the strategy.

Kit design (in order of importance)...

1) Tools = gun, spare mag(s), knife(s), basic gun maintenance kit, knife sharpener
2) Fire = 2x lighter, ferro, tinder
3) Water = stainless bottle, purification tablets, filter
4) Shelter = poncho, trash/contractor bag, space blanket, wool (hat, socks and gloves)
5) Cordage = 325 and 550
6) First Aid = CAT, QuikClot, moleskin, antiseptic, duct tape, sterile dressings
7) Navigation = LED flashlight with extra battery(s), compass
8) Food = prepackaged emergency ration, 22 firearm and ammo, fishing kit, snare kit

If you still have room...

8) Luxury = polypro under clothes, gore-tex rain gear, improved shelter (to possibly include a gore-tex bivy bag and insulated blanket), more wool socks, mess kit, titanium utensil, additional flashlight batteries, additional food rations, expanded fishing kit.

Restated my concerns in EVERY environment (city to country) from a small black out to a full scale break down or invasion is....

#1 = Personal Defense
#2 = Exposure
#3 = Dehydration
#4 = Injury
#5 = Escape & Evasion / Travel
#6 = Nutrition