Old time hoodoo includes many spells for success. However, a look at their methods can be telling. The black cat bone was said to guarantee success -- yet its original purpose was to make a person invisible, and from there it gained a reputation for 'law keep away', 'power' and 'money' because it made stealing more easy. A traditional formula for success was Jockey Club, a fragrance which seems to have come into use because of its association with racetracks and betting upon them (though some bottles did, admittedly, use a horseshoe as their logo, which probably helped its reputation for luck bringing.) Another old spell for success was to get the finger bone of a noted gambler, so his spirit would help you in catching money.
Clearly the notion of success was not that of wealth gained through wise decisions or careful strategy. "Success" was something more akin to a gamester getting lucky at the table or a thief getting away with his crime; the aim was not longterm stability or prosperity but just the bit of luck needed to get through another week. One's own cunning was of little account. Success was about small advantages presented directly from the hands of Fate.
Nowadays, formulas like Crown of Success are often used for matters like success on a test or with a job interview, and while it may be able to help in such undertakings, understanding the perception of success in hoodoo helps to understand what kind of "success" to expect (it is closer to what we'd typically now call "chance" or "luck.") Your interviewer might become distracted and miss bad answers you give, or grow restless and decide to choose someone for the job after interviewing only you and a couple other candidates instead of the dozens he originally had in mind, thereby improving your odds to win. Your success on the test won't be from the magic "bringing out the best in you" but from coincidences effecting the world around you, like the computer slightly misreading your answer sheet to your advantage or time running out before you could lose any points by filling out a wrong answer.
I myself have been disappointed by success spells in the past, but this was again from not fully understanding at the time what should be expected. Something I've gradually come to learn about hoodoo -- and most folk magic for that matter -- is that it's not meant as an aid to those with big dreams or who want to do or have great things. It's meant to get you through the day to day just a bit more happily.