Everything you described is a great gateway drug for GNUPlot :)
Inspired by your example, here's our rolling monthly sums of food expenses, COVID marked [1].
You can see where we moved (temporarily) to a place with lower food costs, and stopped eating out.
But there's also a dip around the holidays, because we spend a lot of that time with family and our food expenses go down proportionally. That dip happens to be consistent YoY, but we don't realize it because we have other things on our mind.
It's just great fun to have this stuff at your fingerprints.