Gonna work on a post! Would've been earlier but I've been job hunting all day in the town my college is at, gotta have some flow of money coming in for my gaming obsessions and books and food of course. Ugh...
I like how food is your third priority. xD
Well there are some things that can improve your odds. The shiny charm for instances are available in both XY and ORAS--you catch pretty much all the pokemon available except a few legendaries and in return for completing the pokedex you can increase your chances of running into a shiny. You could also try chaining or dexnaving, chaining you receive after beating the elite four in XY and dexnaving is thought to to increase the chances of running into a shiny pokemon similar to chaining. You can also use a foreign parent for egg hatching known as masuda methoding which raises your odds of a shiny as well.
My advice for shiny hunting is just to be patient, you could get in one encounter/sr/egg or in 500 or a 1000, but as long as you're patient you'll always get a shiny in the end. Also doing other things while hunting such as watching movie or tv shows are great to keep you from becoming bored.
As for the legendaries: all the legendaries in XY are shiny locked so : Xerneas/Yveltal/Zygarde/Moltres/Articuno/Zapdos are unable to be shiny in those games (though Moltres/Articuno/Zapdos are all capable of being shiny from previous generations) and in OmegaRuby and AlphaSapphire: all of the legendary pokemon are capable of being shiny save for Kyogre/Groudon/Rayquazza and I believe Deoxys is also shiny locked. As far as I know all the other legendaries you can encounter in OmegaRuby/Alpha Sapphire are capable of being shiny.