Start by doing a full clear and farm until you can buy Skrimisher's saber with devourer. When this is finished farm to get as many stacks as you can, and work towards Youmuu's Ghostblade. As soon as you have this item, the cheese begins. At this point in the game you should be able to easily kill the opponents bot lane without any help, as long as they're not fed. Work towards getting your devourer.

You should have your devourer now, and it's a good idé to pick up some boots too. You are very powerful at this point in the game, so you should be able to pick up easy kills around the map. Your Youmuu's and your ultimate combined gives you a ton of attack/move speed, so your ability of assassinating people is crazy. Just remember to keep farming, because you want your Trinityforce before the game goes on too long. When you have Trinityforce you should not have any problems split pushing, since you can mostly one vs one anyone. The next item you want to get is a statik shiv, but it shouln't be a problem since the item is pretty cheap.

In this point of the game you are extremely strong, and you are an adc's nightmare. All you have to do is; activate your ultimate, e and youmuu's then right click them. Most of the time you can just watch your screen as your character runs up the the target and 2 shots them. Getting gold for your infinity edge is easy, and as soon as you've bought it, your power is ridiculous. You should be able to one vs three most people no matter who they send. A few things to remember is that you can easily kill tanks if you smite them and activate your e first. Another thing to keep in mind is that you are very easy to kill. Your best way to stay alive is to kill everyone who is trying to hurt you.

Your very strong in the mid/late game but the pre-youmuu's period is fairly weak. I hope you find this guide useful, as it has been very fun for me to teach you guys this, and i hope you'll have as much fun with this build as I've had. Have a wonderful time on the rift :D