There seems to be almost as many gambling systems as gamblers. There are advantage play methods at blackjack, craps, video poker, casino poker, Pai Gow Poker and, yes, even slots. These can actually work to get the players a relatively small edge. Few players, extremely few, learn advantage-play methods, preferring instead to adopt various betting schemes that don’t work to get the player an edge, which they can’t actually get over the house.
Thus, on the losing end of the spectrum (where just about every player plants himself) you have money management systems, trend betting systems in all their almost infinite variety, (flawed) mathematical systems such as the Martingale, various cancellation systems and on it goes into the light-years equivalent of wrongness.