Brewster's Millions is a film which I only saw recently but has been around ages, originally based on a novel of the same name published in 1902. Since then there have been seven film versions, the most recent version which I watched from 1985.

Based around that old nugget of wisdom that money can't buy you happiness, the story follows Monty Brewster (Richard Pryor) as he attempts to squander 30 million in 30 days, so that he can inherit his uncle's full fortune of 300 million. The only catch (of course there's a catch) is that he can't tell anyone what he's doing, cannot gain any assets, cannot buy expensive things to just give them away and must receive a worthwhile service from anyone he employs. He's also restricted on how much he can donate to charity/gamble away, and if he fails to meet these stipulations by the end of the 30 day stint will receive nothing.
Somewhat predictably the task is a challenging undertaking, and his pals end up inadvertantly hindering his progress by making him money, but our endearing protagonist earnestly struggles on, resourcefully and comically doing his utmost to get rid of his wads of cash. Outdated in some ways (in a good way, who doesn't love that 80's vibe) but not others, this is a great film to watch any time you want some easy viewing/cheering up.