Template:StubTemplate:Character Gabe is a Dauntless born boy. The book doesn't mention him much mainly because he doesn't train with Tris and the other transfers. He isn't mentioned but is said to have been in the ziplining scene with Tris and the other Dauntless borns.
As noted above there is not much about Gabe but it is mentioned that he has metal ring between his nostrils.
The only reason Gabe is mentioned is when Uriah invites Tris for the initiation ritual.