Like many salarians, Giz at a young age spent most of his time building and preforming experiments with many of his fellows - in between studies of course. He was basically that normal salarian stereotypical mold, smart, always ready to learn. It was during this time that he became somewhat fascinated by the krogan race, something that never went away with age. It was also something, combined with his naivety and being a bit too curious, that would constantly get him into trouble.

Learning about other races, wanting to see a real krogan, and generally wanting to get away from a sister that constantly talked down to him, he left his home when he was old enough. See the universe and whatnot. And study, can't forget that.

Throughout his travels, getting into more trouble than he should have been, he showed an aptitude in abilities common amongst infiltrators. His smarts were enough to keep him from receiving any major injuries when he found himself in trouble, and he'd never found himself in a situation he couldn't get himself out of. Brain is better than brawn, but it's nice to have a back up, so he figured learning how to fight would be a good idea.

It was sometime after this decision when he managed to befriend a krogan who then invited him to a firing range - a place where he discovered his first shotgun. The krogan was involved in fighting the reapers, so Giz decided he'd help out and join; which quite possibly caused his best friend - a fellow salarian - to join in as well. THE POWER OF FRIENDSHIP.