Kind of pointless because Life Gamble is more powerful the more HP the poke lost, but I still would like to know.
NO Using this move will not activate the Focus Sash, and therefore, the Pokémon still faints regardless of whether the item is held or not. If the user of Final Gambit has Sturdy, it will faint even if its HP is full. http://bulbapedia.bulbagarden.net/wiki/Final_Gambit_(move)
