Solo- you just keep transfusioning the other champion till you think you will kill them with ease. I prefer the ignite ult transfusion method. This can kill anyone with below half hp.
Mid game- keep leveling get to 18 as fast as you can. I prefer to gank people every 5 minutes. WIth this build you should be a super tank. If done right you can tower dive at lvl 6 with ease.
End game- Run in to group fights after any tank and just start Aoeing everyone you can while transfusioning the enemy champion with the lowest hp.