I haven't yet read any of the 299 Days books yet, so I'm not sure I'm interpreting your question well. However I believe you're basically asking how to get started with some food preps and feel overwhelmed on the topic?
I don't have a 1-2-3 guide, but I can tell you what I did. My wife is lovingly tolerant of my prepping but doesn't really get involved too much although she does appreciate my efforts to "take care of us if the world ends". I took a two-forked approach. On one hand, we did some basic cost analysis and I got her interested in buying in bulk when items, especially canned goods and dry boxed goods, were on sale. We're both pretty frugal and it took awhile for her to see the longer horizon. I setup a big shelf in the basement to keep it all on and kept it organized for her. She actually got into it and was really excited when she scored a great deal. Additionally, IMHO, as a prepper one of the best ~ $50 you can spend is for a Costco membership. You can buy cases of canned beans, bags of rice, 4lb boxes of salt, etc. We incorporate most of that kind of food into our diet. Another way is instead of buying the small sack of flour or sugar, buy the industrial size at Costco. It'll keep for quite awhile. My wife likes to bake so instead of her getting a 1lb bag of flower at the grocery store, I get her a 20lb bag at Costco, fill her crocks in the kitchen and keep the rest sealed up in the basement until she needs a refill. Takes her a lot longer to go through, I have some storage-grade food on hand at all times, and it's actually a better cost-per-pound which rolls further into the food buying.
On the other hand, I was where you were about a year and a half ago. I wanted to do something and I wanted to do it now. So I decided to just sink the cash into a serious cache of long-term food. I bought white rice, black beans, red winter wheat, oats, salt, and some powdered milk. Packed it up in mylar bags inside of five gallon buckets using the dry-ice packing method and stored it. I have enough food (sans a meat source) stored for 1 year for the three of us (me, wife, daughter) or less to feed immediate family or close friends. That will get us through in a really tough situation. I'd still need to deal with meat and fresh vegetables, but we could live on that if we had to. It was a pretty expensive up-front proposition, but packed properly isn't one you'll have to repeat too often. I think "eat what you store, store what you eat" has its place but I don't find having a long-term "deep larder" to be a bad thing either. I think people need a mix.
If you're stuck on how to move forward, consider this... Take a run to Costco or Sam's Club or another warehouse style club and pick up some bulk staples like a 50lb sack of rice, a couple of cases of canned beans or other veggies, some salt, a jug of honey, some olive oil, and maybe a few other dry goods of that kind. Just put them away in a cool dry place and try to ignore them for a little while. And I mean literally put them away - don't keep them in your cupboard/pantry or where your other food is - maybe make it hard to get to - break your self of the thought it's food for regular eating. All of that stuff will keep as-is so just let it sit for a bit. Get comfortable with the idea how you can keep your regular shopping schedule while buying more of the stuff your normally buy that stores well. Work on that for a few months, try to build up a stockpile of your daily routine items that store well. If a disaster strikes "right now", you can take comfort in the fact you have something squared away. Look into ideas for long-term storage, maybe pack some buckets with the stuff you bought and haven't touched yet. Get comfortable with the concepts and don't panic.