First thing to know in an emergency is that it's OK to fast. Generally if you're in good shape, you can fast easily for three weeks. So first off you need nothing or very little. You do need water however - that's a problem. So think about water.
As for food, the highest calorie, salt and fat food you can get is Spam.... and you can get 8 cans of it at Costco for about $20 or so. This is month's supply if food if you really ration it out. This saved a LOT of lives in WW 2 as a can will feed a whole family for a couple days. And it won't spoil once it's open as there's so much salt in it.
So for emergency food, don't worry about anything like green beans which are low calorie. You want HIGH calorie - lots of salt and fat - just the stuff they tell you that you're not supposed to eat otherwise.
Water.... remember that there's 2 or 3 gallons water in the toilet tank - and there's 40 or 50 gallons in the water heater. So in an emergency, you shut off your water supply which might be polluted - and isolate these two sources of water at least. If you can, you fill up every jug, jar and bathtub with water before you shut down your supply.
In a real emergency, the water will often be diseased - with perhaps cholera which is deadly if there's no doctor. So you want just a tiny bit to eat - stuff you don't have to cook - and as much clean water as you can keep.
Think ammunition too... 9 mm is good - .22 is good. You can use it or trade it for more food.