-Rayquaza: after you have gone to sky pillar once and called rayquaza to sootopolis city you can get rayquaza lvl 70 there.
Kyogre : after finishing Pokemon league go to the person in the weather institute who gave you castform and talk to him. He will tell you there is very heavy rain in some route. U must dive in one of the dive marks in that area. Go till the end and there will be a cave called marine cave. In the end of the cave there will be kyogre lvl 70 .
Groudon: after catching or defeating kyogre again go to the guy in the weather institute and talk to him. He will say there is bright sunlight in one area . Go to the area. There will be a cave called terra cave.there will be a lvl 70 groudon waiting for you .
Rayquaza is found before the E4 and G and K are after game