I don't know that we ever saw a pre-Phyrexian Gith. Maybe he hadn't been modified yet, but he was one of those monks who worshipped the artifacts and had started installing them in his own body hadn't he? I don't remember there having been a time when Phyrexia didn't have its hooks in him. Geth by contrast started out as a purely selfish warlord, long before Phyrexia displayed its presence on Mirrodin (ie before they retconned it as having been present all along).
Gix was Yawgmoth's greatest enemy in The Thran. His role is sort of an evil opposite of the one that Green Arrow played in JLU