AT the start make sure you get your items, which ever is best anyways. After you get into lane and minions spawn you want to start harrassing your laning opponent as much as you can, because your w will be a spike in your damage. In lane you want to always use your w on them with full ferocity. Try to score some kills and maybe even roam. If you notice you're about to get ganked, try to look at their health, because you can easily turn a gank around.

When ever you roam, always try to go for kills, not just a gank to get them to flash. You have to make sure you secure that kill, because you can only use your ult so much. Make sure you use your dfg right before you jump on them.

When it comes to team fights, you don't want to show yourself unless you're going to siege. Try to be that assassin that one shots someone when you use your ult. If you can get that squishy target that is in the middle, you will do enough aoe to where your team can follow up and secure the win for the team fight.

When it comes to late game, if you want to make a change to the game or secure that win. You want to catch the squishies that are by themselves. Your ult will be up much faster. This way if you burst someone down but they escape but waste summomners, you can do that and secure that kill. This way you can help your team win the game.