Even the United States government recommends that its citizens be prepared for an emergency by having a three day supply of necessities on hand. The food supply chain in the United States could handle only about three days of no trucks delivering groceries to the stores. Few people realize how intertwined everything is in our economy. It really wouldnt take much for our society to collapse.
If things really do get that bad it will be very important to be prepared for more than a three day emergency. You should begin now by building up a reserve of items good for bartering in times of societal collapse. Start early and build up slow and it wont a significant budget issue at one time. Doing it know why things are readily available will be much easier than trying to obtain the needed items after a societal collapse.
Primarily stockpiling items that you use means you will be able to work your way through them keeping the items fresh. A side benefit of this is that should you have a personal crisis, like becoming unemployed, you can put off buying some of the items until you find another job. You can also hold out for the best deal on the items and then purchase quite a few at one time, this is a technique used by extreme couponers.
There are some other things that you should consider doing before an economic collapse, like learning some appropriate skills. Skills for surviving an economic collapse will not only aid you, but if you havent built up a reserve of barter items, you may well be able to barter your skills for something you need. Learning some of these skills can be even more valuable than building up your barter items.
With the appropriate skills you will continually be able to obtain or make items for barter. After an economic collapse many old fashioned type skills will be in very high demand. If you can grow a garden and preserve the bounty you will always have food for yourself and hopefully some extra to trade.
Its unlikely that you will be able to become proficient with all of the skills needed after an economic collapse, but it will be good to be somewhat familiar with many of them. Learn some basic first aid before its required of you, always a good thing to know anyway. At a minimum collect some resources to aid in learning the skills, in the form of books and/or magazines. Dont just assume that youll be able to just search the Internet to learn how to do something, if theres not electricity there will be no Internet.
Working on both, collecting barter items and learning survival skills, before an economic collapse will be much easier than trying to do it after one. Using your barter stockpile as a buffer against higher prices and allowing bargain shopping can help before an economic collapse. And using the skills needed to survive an economic collapse as a hobby or even small business can also benefit you before a collapse. That artisan bread baked out of your homegrown wheat in an earthen oven can sell for a premium before an economic collapse, after, it may simply be food, but everyone will want it.