According to some sources, Scrooge's Dime is the force behind his three cubic acres of money. In "Lost Beneath the Sea" (US-01) Scrooge looses his Dime, and he immediately starts loosing money until he regains it. Other sources, like Don Rosa, lets Scrooge state that he made his fortune by being "harder than the hardies and smarter than the smarties, and I made i square!" We find one example of this in chapter 12 of "The Life an Times of $crooge McDuck" (D 93488). Donald says: "Look kids! This must be the famous lucky dime... the charm Uncle Scrooge used to get his entire fortune!" Scrooge replies: " 'Lucky' dime? What thimble-headed gherkin invented that supreme bit of absolute baldeash!... I had that dime for 20 years before I struck it rich! And when I did, it was through my own hard work! Period!"
Still, good and bad luck is no coincidence in Duckburg.

Things that bring luck

Even though Scrooge did not need the Dime to get rich, some of his belongings are vital to his wealth. In "The Magic Hourglass" (OS 291) Scrooge gives away an old hourglass to Huey, Dewey and Louie. Soon he starts losing money - the hourglass is one of Scrooge's charms. He has other charms, but the story does not tell us more about them. One of the charms is probably the Ganesha amulet we see in "Treasure of the Ten Avatars" (D 95153). Ganesha is an Indian god of success. In "Two Way Luck" (US 31-04) we learn of Scrooge's belief in astrology, horseshoes, four-leaf clover and Friday 13th.

Donald believes in charms as his uncle does. Once, in "Wishing Stone Island" (WDC 211-01) Donald sells his house to go looking for some mysterious black wishing stones mentioned in a fake radio transmission.

He does not, however, believe in the rabbit's foot an Indian (of the native American kind) gives to Huey, Dewey and Louie in "The Rabbit's Foot" (WDC 32-02). A book tells him that things cannot bring luck. In the start he believes what the book tells him, but later he changes his mind. This story is probably important for the belief he shows in "Wishing Stone Island" (WDC 211-01).

Gladstone Gander - luck incarnate

Gladstone Gander is luck incarnate. He is one of the most unbearable persons in Duckburg. Flintheart Glomgold may be more unbearable, but he lives in South Africa, and not in Duckburg. Although the Bible tells us otherwise, all true donaldist rejoice when Gladstone is out of luck. Barks created Gladstone to have a character to torment Donald, and as a contrast to his bad luck. Gladstone is Donald's antithesis regarding luck, as Scrooge is regarding money. It is impossible to feel anything but disgust towards somebody who is ashamed because of the one one day he worked. Gladstone has put the money in a safe to make sure nobody finds it out (WDC 140-02).
Why is Gladstone lucky? Astrology is presented as an explanation in "Luck of the North" (OS 256-02) - Gladstone was born under a lucky star. The belief that the stars influence our lives originated in Babylon where people believed the stars to be gods. We now know that the stars really are great balls of fire. Astrology is superstition. (May the sky fall in our heads if astrology proves to be correct).
In "The Lost Rabbit Foot" (OS 1047-05) Gladstone has switched to an alternative theory. He now believes that a rabbit's foot causes his luck, and he asks Gyro to find the it. Gyro proves that Gladstone is wrong, but Gladstone has one last theory, presented in Don Rosa's "The Sign Of The Triple Distelfink" (D 97437). In this story we are told that Gladstone is the most unlucky person in Duckburg on his birthday (this should refute the theory that he is born under a lucky star). Gladstone is exposed to several wonderful accidents. I do not understand how anybody can stay an atheist after seeing Gladstone's bill squeezed between a window and its frame. The reader does not stay long in paradise - Gladstone is freed from the curse of his birthday and ends up lucky all year.
Anyway... towards the end of the story we are told that Gladstone is lucky because he was born on his mother's birthday, and she was lucky because of a painting on Grandma Duck's barn.