I would choose Edward Elric... Prior to beginning his alchemy training his teacher Izumi Curtis left him and and his younger brother Al stranded on an island in the middle of nowhere for a whole month.
He's the perfect candidate because he's already experienced this scenario before plus he was much younger when it happened and since then he's grown up to be a capable young man, so he'd definitely would be able to help me out. And although he gave up his alchemy in order to get Al's body back we have to keep in mind that he didn't always know much about alchemy. Through his journey he gained profound knowledge as well as several survival skills that would come in handy.