Good natures for Gible: Adamant, Lonely, or Brave. All raises attack, which Gible has high attack, a boost in that will make Gilbe better. Never get Hardy or Serious, the negate themselves.
Recommended Gible egg moves: Iron Head, Outrage, Sand Tomb
Good natures for Growlithe: Brave, Mild, Quiet, or Rash. Growlithe has a balance physical and special attack, so any of these are good to raise one and not hinder the other.
Recommended Growlithe egg move: Crunch, Flare Blitz, Close Combat, Heat Wave, Morning Sun
If I'm going to give my Gible nickname it would be something like Gargoyle or Chomp-whomp. Something that relates to Gible.
This answer is my opinion and there might be a better answer.