Carrying cash is very dangerous these days due to "guilty until proven innocent" asset forfeiture laws. That said, having a small stash of cash (something you can afford to lose) for emergencies is wise. Food is most important, though. I always have at least 25 lbs bag of rice on hand, as my basic staple. Along with the other food in my RV we're good for a month or more without supplementation. We start out with 81 gallons of water when boondocking, so rationed, that can last a while too. It all depends on how long you think the collapse will last. My RV uses regular gas, which will be easier to find than diesel after a collapse, but it will still be rare and pricey. It's best to bug out to a "safer" area, find a good boondocking spot away from population centers and near water (where there's fish, foraging and game, if possible) and hunker down till the worst of it blows over. A water filter is a worthwhile investment, even if it's just one of those survival straws, just to get you through the worst of it, as most of these kinds of things end quickly - no more than a month or so. But just a few days without water in the desert can be a severe hardship, if not fatal.
I used to have a couple bug-out bags containing 3+ days of essentials, but since I have aged, I find this impractical as I am now tied to my RV. I go where it goes. Also my threat assessment has changed over the 20 years since I left the Army - I no longer consider a nuclear or chemical emergency/terrorist attack a high enough priority to prepare for, as I once did. It's good to go through the mental "what if" exercise even for what you may consider extremely unlikely scenarios, such as an EMP attack (which would make credit cards useless for a very long time), nuclear or chemical spill from a train wreck, plant explosion, etc,. to a simple monetary collapse, hyperinflation or devaluation of the dollar due to a trade war, natural disaster, or any number of reasons.
As a Hurricane Katrina survivor, (I've actually lived through several hurricanes.) I've seen the total devastation of an entire region of the country, where my banks were underwater (literally). I went into a home depot in Florida to buy a small generator and my debit card was declined because they had no way of verifying funds. Luckily I had my inlaws there buy it and I reimbursed them. But what do you do when this is not possible and you need food or other essentials? Coming back most gas stations were closed because of no power, and the ones that were pumping gas (as they had a generator) typically had a 5 gallon limit and all were cash only.
I do have some precious metals, gems, and jewelry but you will only get a tiny fraction of their value in an actual emergency if it is severe enough to require barter rather than dead presidents. In desperate situations like this, remember safety is paramount because "zombies" (folks who who don't prepare and who are in desperate need) will resort to violence to take what they need. Think post-Katrina marauding gangs and martial law in New Orleans and the surrounding area. I lived through earthquakes and riots in L.A. too - not fun. Remember ammo will get you food (or let you keep what you have) easier than food will get you ammo.
Chip