Since you already have the lucky Kyogre, I probably wouldn’t be in a rush to evolve either, tbh. Plus, you already have a fairly high level Gyarados with the right moves, and it’s IVs aren’t exactly abysmal.
Now that Groudon is gone, there isn’t much coming up that we know of that Water-types will be needed for. I would save your dust for now, and worry about making another Gyarados when you feel that you’ll need another. By then, who knows, maybe you’ll end up catching a high level weather-boosted Karp, and save yourself a ton of dust/candy.
Should you not find a better Karp by then, I would personally go for the lucky one. It will have slightly less bulk, but it’ll also cost you significantly less dust to power up.