I would get rice, beans, canned tomatoes, and some herbs/spices along with a book on foraging edibles plants.
Radishes and spinach grow super fast. Chia seeds sprout fast.

Depending on your weather, think about what you could grow. If you have a window seal, you can plant basil. If you have a grow light or aerogarden you could do tomatoes inside. 4th of July puts out lots of little tomatoes faster than anything.

If you were buying green onions, don't throw any away but plant them. Plant your celery bottoms too after you soak them when they get roots. Start drying any extra veggies you have leftover from meals. If you have bones, put up stock.

If you can't buy and bring in then focus on wasting little and putting up extra.