Thanks for posting this. It's a great reality check. I started with an initial investment to cover some basics and have been a prep 'grazer' ever since. When hot sauce is on sale I pick up an extra few bottles. Buying stuff on sale really starts to add up the savings after a while, rather than an all-out panic buy at the last minute which is always too expensive.
On the long term list I would include some quality garden tools that will last a while or can be easily repaired. Also having a good compost pile up and running is a great way of turning food and yard waste into free fertilizer, and it's a lot easier to set it up now rather than after an emergency when things like apple cores, orange peels, and grape stems start to look more appetizing. In a SHTF scenario you can even put spoiled meat in the pile. Enough carbon in the form of leaf litter on top will filter out the stink, or leave it uncovered to attract the cats, rats, and mongooses for some extra protein in your diet!