There as many theories as there stars it seems. I too take a practical approach. I grew up on the streets and graduated college when I was 50. I think that your experience will better serve you than any economic theories. Theories are just that, when you're dealing with everyday dollars and cents common sense works best. I wrote this some time ago.

https://steemit.com/life/@richq11/the-economics-of-earl-common-sense-and-the-zen-of-joe-sixpack