Tobacco and alcohol are good. Whiskey keeps longer so I keep a few bottles around and I am not a drinker.
Ammo, I will just say I have plenty and let it go at that.
Food, I am buying up more can food each payday. Get stuff you like and eat regularly and avoid buying stuff you think you are supposed to.
Junk silver coins (old worn silver dimes, quarters) are cheap and good for possible barter. Some gold too in smaller quantities.
Do you have a way to fortify your home. If not, you can be quickly overrun. Precut wooden barriers for windows and doors minimum.
Size up your neighbors for what they can bring to the table. Can they help with defense, medical, etc or are those just going to get in the way. Sounds harsh, but survival may depend on it.
Whatever medicine you have is almost surely not even remotely close to being enough. Stock up, then when you think you have enough, double it at a minimum.
I buy all my antibiotics here without a prescription, I have done so for over 15 years. I have a sizeable stash of everything.