I don't really think money matters. I keep seeds on hand year after year. I not only collect them from the garden but when the stores sell out at the end of spring what they have left 5 for $1 I buy up about 40 packs. Even if it is stuff I don't like to eat I buy the seeds up I figure someone may want hot peppers or broccoli. Plus beggars can't be choosers.
The best advice I can give you is buy 1 extra every time you shop. Buy 1 extra salt, or 1 extra baking soda or whatever that you may need some day for food ( not one of everything all at once. Just 1 extra item per trip), cooking, baking, and so on. Use dollar stores for lots of things like batteries, and extra items you may need. I know that is what I do. I even have bought tools when they are on sale and just add them in the barn 1 every few months. They have come in so handy lately, when my husband up and took off he took all the tools with him, so now I am having to restock the shed and barn. I got me a new saw and a new drill/driver last month. I also have bought a new hammer, and loads of nails and screws.
I met a lady about 5 years ago that said keep an empty bucket in the kitchen and buy can goods that you normally use and dry goods that you normally use daily and fill the bucket little by little when it's full close it up and hide it in the closet. Repeat it again and before you know it you will have enough food stored away to last your family 3 to 6 months.
So far I have 2 family meal buckets put away, 1 bucket of rice, 1 macaroni, 1 beans, and another full of Ramen noodles. That is just the food. I then have 1 full of soap, shampoo, hand cream, and other things that will come in handy. When you pack that family meal bucket make sure to add in a bag of hard candies for the kids, and some granola bars for the adults. Fruit rolls also come in handy in the buckets.