Gale hunts with Katniss , They take the risk of breaking the law. Which makes him fearless. Like for example when Gale hunts a squirrel and kills it. Then, he trades it for a loaf of bread. That makes him fearless.

He's trustworthy because when Katniss volunteered he grabbed Primrose so, she would be safe., Then when it was time to meet Katniss he promised to take care of her family and especially his family.

in the mocking jay he works as a coal miner for 12 hours a day and takes care of Katniss's family.