It's been about 3 days since I got my Kyogre on Alpha Sapphire. I'm starting to get worried because his growth rate is slow and I really want to challenge the Elite Four soon, but he's only grown 4 levels,and I've been playing non-stop.
Keep re-battling trainers using Trainer's eye on the AreaNav.
I got Groudon to level 60 this way. Might take 2-3 hours, but hey it's worth the wait.
Hope I helped!
-It's a secret!
Put the lucky egg on him, and you can use the exp point o power too. Also, a good place is to battle and rebattle rich boys, alternatively use random secret bases that you can find. You can switch grind, but that may take too long and be uneccesary.