Breeding shinies doesn't increase your chances of hatching a shiny baby; breeding two Pokemon from different language games does. And it only decreases chance to 1/2048. You're probably thinking of the original GSC games, where breeding shinies did have an increased chance of hatching a shiny baby. That changed in gen 3 when shininess was no longer determined by IVs. And shiny Magikarp are gold, not blue. --- It would appear that I have been driven to madness. Probably would have been faster to walk.
Normal chances of finding a non-scripted shiny (either wild or from an egg) - 1/8192 Chances of hatching a shiny egg from two shiny parents - 1/8192 Chances of hatching a shiny egg from two parents of different languages and regions - 1/2048 --- I love girls with leprosy...that way I can take some home with me.
You could also try your hand at RNG manipulation. It's probably your best bet in HGSS, especially if you don't have different language pokemon to breed with. Otherwise, be prepared to waste a lot of time before you finally find a shiny, if ever. --- XG Rock on.
Basically it's a method of manipulating the game into giving you shiny pokemon, pokemon with perfect IV's and the like. It takes a bit of practice, and you need a lot of things in-game for the initial set up, but I've hatched quite a few shinies with it. Look for some tutorials on smogon. --- XG Rock on.