I have actually been through various crisis situations such as being described. Only once did I actually "need" a weapon and that was during Katrina. Even then I didn't need some fancy ass AR (Rather ironic, I did have one but it was one of my guns that never came out), a shotgun slung over your shoulder so that your were visibly armed was by far the best "defense".
In every other situation I never needed a gun, albeit I had one, but I did need my food and water. Knowing that I would say that food/water is definitely a priority before a gun and when you do get around to defense a simple and cheap pump action 12 gauge is absolutely perfect.
With all of that said, neither food nor guns/ammo are the most valuable things to have in a crisis. Without a doubt the absolute most valuable thing to have during a crisis by far is fuel, usually in the form of regular old gasoline. I have gotten guns, food, water, offered sex from someones wife, gold, untold amounts of cash, you name it for relatively small amounts of gas. People buy their nice fancy generator for their house and then they buy one or two 5 gal. cans of gas for it. They don't fill up their vehicles or waste half the gas in it looking for other supplies they didn't stock up on and until power comes back on you can't purchase gas with any amount of money. After refusing $10 a gallon a guy offered to let me bang his friggen wife for 5 gallons of gas!
I keep a few weeks worth of food (easy as hell), two weeks of water (a bit more space consuming) and of course ammo for all of my guns but I also keep well over 100 gallons of gas at all times. The gas is a bit more of a pain in the ass because you gotta keep rotating it into your vehicle but when/if you ever need it the trouble will be well worth it.