i started doing this many years ago. it’s easy.
every time i come home and put my purse away for the day i check and see how many dollar bills i have. then i place anywhere from one to three dollar bills in a secret place and leave them. the next day, i do the same or whenever i can. saving one or two at a time i find i often have enough to supplement my gasoline bill before the end of the month or week or whatever. also nice if a friend invites me to lunch!:)