Ok it's not like trying to fill out Gambit's history is the easiest thing in the world but I'm going to give it a shot so humor me.
When Gambit was a young child living in New Orleans he tried to pic the pocket of a certain Jean Luc LeBeau who was the leader of the Thieves Guild in New Orleans. LeBeau took a liking to the child and adopted him. While growing up Remy met Bella Donna Beaudreax of the Assassins Guild and they became friends. The Thieves guild however was always at war with the Assasins guild so the two guilds at an attempt to make peace arranged a marrage between Remy and Belladonna Boudreaux who was the daughter of the Magnus the leader of Assasins leader. Belladonna's brother Julian hated Gambit and the peace that was brought by Remy and Belladonna's wedding. Julian eventually challenged Gambit and he ended up killing Julian. Gambit was then expelled from the Thieves Guild to keep from breaking the peace.
After leaving his home Gambit and he took up being a thief he was also a mercenary who took up several jobs which lead him to meet Sinister who hired him to do various odd jobs. Gambit's final job with Sinister was being hired to recruit the Marauders and lead them to the Morlock tunnels in which he became involved in the Mutant Massacre.
After that Gambit started stealing from other thieves he would often steel the goods that had been stolen from someone and return them to their rightful owners. During one of these cases he met up with Storm who had been reduced by a child form by The Nanny. Gambit ended up saving Storm while he was robbing the Shadow King who was after Storm. Eventually she took him back to the X-Men.
Gambit eventually became a member of the X-Men but was never really trusted by them since they knew nothing of his past and Bishop was constantly accusing him of being the X-Traitor. The X-Men eventually found out about his past through the trial of Gambit in which Eric the Red revealed to the X-Men Gambit's involvement in the Mutant Massacre. Rogue then left Gambit in Antartica, where the trial took place, saying that he didn't have a home with either her or the X-Men and that if he wanted to live then he could fend for himself. Well that's not exactly what she said but basically.
