Important detail: since you need 3 marks to stun someone, you can only start stunning people at level 2 (unless you start with W, but it takes a long time to get the stun); I'd suggest you only agro on the enemy one you get level 3, because then you have 4 potential marks in your combo, that makes it so you don't lose instantly if you miss your Q; starting agro at level 3 is also better because you can stun both players in the enemy bot lane, by with your E, W and then using your W's passive and Q each on a different player.

Start being oppressive from level 3 onward, be the guy who runs and starts the fights, use your ult and flash like those didn't have any cooldown; make sure your team fights every dragon, because the moment you get your ultimate, you can already start stunning all 5 enemies 2-3 times, dragon/baron fights are awesome for this build because everyone is very close and you can easily stun everyone.

Once you have your Zhonya's up, play like it's blind pick, be aggressive and don't let the enemy fight, always be with your team, it's almost impossible to win against you if you have a dps with you; and if eything goes wrong, just E away and watch them as they get smaller and smaller with distance.

Have fun.

Btw if you have any questions leave them in the comments and I will try to answer them if I remember to.