You can only be prepared to the degree that you can afford.
Even so, such preparations are only of a temporary nature with a finite supply.
Once you run out of stuff, you're done.
Everyone should have some food, portable shelter and water or means to purify water set aside that will allow you to survive without outside aid for a few weeks or months.
Above all, it is WATER that you need. Americans take this for granted but should the municipal water treatment plants go down this place is no different than any third world shithole where the water can kill you.
Anything more is just pathological. You cannot set yourself up to survive TEOTWAWKI.
I want to re-emphasize this water thing. It is the water that is heavy and bulky and difficult to transport. It is your water supply that will fix you to your current location as long as your home is still standing. In a natural disaster you can replace your home. If it is TEOTWAWKI and you lose your home you are a refugee.
Welcome to the 21st century, things are going to be very different.