Based on how I started and where I'm at now for a family of five, I would suggest starting with buckets of rice and flour along with vitamins first. Rice can be had from places like BJs for $50/100lbs. About 33lbs will fit in a 5gal bucket sealed in Mylar. Same for the flour. Mylar bags btw can be sealed with a common iron. Bulk vitamins, including chewables and the gummy bear types for kids can be found on Amazon for very reasonable prices. IMO you should have vitamins stored for longer than you plan on having for food, especially for children.
Learn how to make your own bread and do it regularly, at least twice a month.
Simple recipe here. Stock the ingredients necessary to do so. Buy bulk dry yeast, not the packets which are a complete ripoff. Have a way to reseal the yeast. Once you know how to do this stock Peanut butter and preserves. Ta da, sandwiches. I think I ate peanut butter and jelly for at least grades 1-6, so I'm pretty sure you can live on it
When you go shopping buy extras of things you normally consume like canned vegetables, tuna and pasta.
Buy bulk spices and baking ingrediants like vanilla, baking powder, etc from places like BJs. Never buy these from a regular grocery store, it's far too expensive.
We cycle thru our supplies, but have a rule that if we "run out" upstairs and steal something from the store room you write it down on the list and replace it with no less than two. This prevents you from getting into bad habits and "stealing" from yourself.
Definitely learn how to can and have a garden. Grow it with heirloom seeds and learn how to harvest your own seeds.
Go to a LDS event. Many here have been to more than one.
Keep at it and ask questions. I think the worst part is the more you try to plan, the more you feel inadequately prepared. It helps to remember you're trying to do something, which is more than 95% of people.