Honestly, if you are stuck in Bronze 4, that means you deserve to be there. Your best bet is to get better individually. Lee Sin is a jungler who should easily be able to snowball the game out of control if you are good enough with him, so if you improve you should easily be able to rise. You should probably improve yourself outside of ranked(normals/draft) so that you can be more willing to take risk. There won't be as much pressure so you can try things you potentially wouldn't in a ranked game because it can cost you the game.