Easy:
20" 12G Mossberg 590 with a 7 round tube loaded with 1oz rifled slugs
Slightly more:
1 AR15 per adult, minimum 10 loaded mags per AR15, plus a boatload of training ammo.
Even more:
Full sized side arm with at least 15+1 capacity of 9mm on a battle belt with first aid, light, tourniquet, knife, EMT shears, two pistol mags and maybe two rifle mags depending on your girth.
At least 1000 rounds of legit defensive ammo per firearm, though, you don't tend to need that much for the shotgun.
But always first aid, always with training, always with dry fire practice.