I really hope Garble matures out of his current jerk state. I think he has potential as a supportive dragon to his kin. (This statement is based off his acceptance of Spike into the group, which is the only thing keeping me from hating him.)
Hey, there's not much Garble artwork out there, so for what you did, YOU DID AWESOME, HEHE YEAAAAAAAH~ There's no doubt a dude as cool as him would win Rarity over. Sorry Shrimp... err, Spike, This ruffian is just a better friend.
Second here. I'm actually one of the few people that like him. He has a special place on my favorite character, as I used to be a hater at one point. I completely understand where Garble is coming from when he hates ponies, G3 Sucked, and it left a stain that isn't exactly easy to wipe off.
I think Garble isn't all that bad. He kinda stuck his neck out for Spike if you really think about it. He didn't have to give him all those chances. Garble is clearly the leader of the group, but also clearly not the strongest, seeing how the brown dragon seemed to dominate all the competitions. He could have lost face among his peers for cutting Spike as much slack as he did. In the end Spike turned against him, which was unacceptable to him. I personally think that if the ponies weren't involved, Spike would've gotten a beating, but I doubt he'd have been seriously injured. They would have just put him in his place. The teenage dragons seemed to have this bro code going on, so it is possible that Garble would want Spike back in the gang. He was their rookie dragon after all.
Garble wasn't a complete idiot and it is likely that he figured the ponies have messed Spike up in the head. Spike did tell them where he's from, so maybe...