They are exactly the right size to hold 32 1 lb cans of food. 4X4 in the bottom, two layers.
And they are stackable and almost indestructible. and have handles if you need to bug out quick.
Then start throwing extra cans in the cart every trip to the grocery store. (Start with the biggest cans of peanut butter you can find).
We also have a monthly delivery of about $100 worth of freeze-dried meat from "Shelf Reliance" each month. That's for putting into the beans and rice so that it's actually edible (and it also has an extremely long shelf life).
Next, set your sites on a "Big Berkey" water filter with at least 4 "Black Berkey" filter elements. That'll go a long way towards taking care of the water need.
Once you've done these fairly modest things you can at least breath a little easier.
BTW, it's also good to put back a good supply of raw honey (preferably from a local beekeeper). Also some candy bars might not be a horrible idea to put back just as a pick-me-up during difficult times (I've read that suggestion several places).
Forget precious metals, but there seems to be a concensus that in the worst case that bullets will make a decent medium of exchange.
I've been preparing since Nov. 2008, and I still have plenty more I need to be doing. This is at least a start. Once you do get started...just keep at it. We may still have a couple of years before the wave hits.
See, there is one thing missing from this discussion. That is the fact that things may not be all or nothing. Yes, we must prepare for worst case scenario. But it is prudent to prepare for the really bad, but not worst case. There are degrees of bad in which precious metals may be very useful.
We must prepare for a range of scenarios. Mad Max isn't the only thing we may be facing.