If you really want to prep for DOOMSDAY, then I reckon your best bet is to start hoarding fuel.
I don't think anyone believes that the fuel price will go anything but up in the future so even if Armageddon doesn't happen you can still just use you stockpiles for day to day usage and save money anyway.
If the economy collapses you will be able to sell fuel (probably at a premium) or you can use it yourself to wander the barren wastelands a la Mad Max.
Stockpiling fuel is the only rational decision.
