Chapotraphouse

Neutral oil. Very calorie-dense, you need it for lots of culinary purposes, and if you use it judiciously it can last a good while.

Salt probably won't get expensive but it's an important thing to have plenty of.

As has been said, storage and processing are going to be more of a financial hurdle than the food itself. I like to buy big glass jars (quart-size or bigger) to put stuff in.

If you haven't already, buy seeds of things you want to grow. Find a balcony or south-facing porch to put pots or buckets on, or locate a nearby abandoned lot to grow things on. Veggies will have much more substantial price shocks.