One Piece-My idea on why Luffy is going to fine one piece.

Ok, Gol D. Roger buried one piece, Shanks was on Roges ship as a kid, Luffy became a pirate because of Shanks, And Luffy is following Roger's Route.

and he's probably gonna find it because the main character always gets what he wants

Not allways, in the case of yusuke he was pnce human protecting the world than he found out he was part demon.