Definitely try out the Friend Safari, as was mentioned. All evidence points to an increased shiny chance there. You can also try out Chaining and Chain Fishing. If you want a shiny and don't care what it is or what nature it has, definitely chain fish. Most people get a shiny before a chain of 100. If you want a shiny that can be found in the grass and you want a certain nature on it, try regular PokeRadar chaining. I've had great success with it, but it takes a little bit of practice to get used to.
You can also try using the Masuda Method to breed, but this is more time-consuming than the other methods. However, by using the Masuda Method, you have more control over what nature, IVs, and abilities your shinies will have.
Right, that all makes sense! Thanks, appreciate it!