People will say:
Gold
Silver
Ammo
Guns
Food
TP (the most under-rated of all)
You need all of these.
I think training would be the best. Reading books on SHTF, medical, farming/gardening, edible plants, mechanical, etc
The list of "what do you need" is endless.
TP. Amen. Sure you can live without it but awfully nice to have.
-d