Most bags I see have too much of the wrong gear; my rule is "Plan first; then pack."

Before you begin you BOB, GHB, or other bag, think about:

1. Whats your situation? Age, health, environment, resources
2. Where are you? Environment, season, geography
3. What is most likely? Zombie attacks are fun, but not likely
4. What is your goal? Stay safe? Get home? Re-start civilization?

Additionally, don't take the coolest gear nor the most tactical - most useful things are very boring; a cell phone charger, a jacket, $20 and water bottle will solve most everyday problems.

Much of what I see - especially online - is nonsense.

+1 to this! It seems like lots of folks and companies assembling kits seem to start with a bag or pack they want to use, then stuff things in til it's enough to sell. To me that's putting the cart before the horse! You need to think about what you need first, then find the appropriate pack.

Also, I learn toward big day packs or hiking backpacks; going for durability and quality - often used. Models like North face, or Deuter.