if i were you i'd forget luk/int for the bird. you'll see a much higher damage increase if you put all your stats into dex. (because the bird wont attack often, but if you up dex, every arrow will do more damage)
as far as the gakkung goes, the absolute best i believe would be Doppelganger/Turtle General, but you'd never want to do that. The best bow (short of SQI artemis) is a +10 Composite Bow with Doppelganger/Doppelganger/Turtle General/Turtle General. Those are all MVP cards and that bow will run you around 72 million zeny.
Right now, i'd reccomend you upgrade your bow if you havent already, artemis should go to +4 safely (if i remember correctly) and that will give you some bonus attack points.
As far as carding the gakkung, i'm not sure. If you're dying to put something in there, two andre cards would give you a nice attack bonus. You wont want to use Doppel or Turtle Gen cards in that bow because it's a waste, you're better off putting them into the 4 slot composite bow i mentioned earlier.
I'll reccomend to you also: You should buy a Hunter Bow in the Payon Weapon Shop. It's higher attack than a gakkung. I used a +5 hunters bow untill i got my DDTT Composite and it worked just fine.
