Hey guys, this is my first build, so this might not be good lol, but here we go!

Pros:
-High early damage
-High late game damage
-Can carry easily
-Nice initiator

Cons:
-Squishy early game
-In my opinion his ult is only good if you're going after heroes, cause you throw them in the air and helps your teammates to kill him.

I like the AD Quintenssences at the beginning, cause it helps a lot your damage early and late game.
The armor penetration helps at your early game, and can help at your late game.
And the Magic resist and Armor runes are perfect for early game + the magic resist per level helps you late game.

I prefer to start with a doran's blade at the beginning to improve with your Quintessences of AD.
Then I just get a Boots of Speed, and rush for Trinity Force, it helps at your damage, can slow your enemy, gives you a helpfull attack speed + the effect of Sheen.
Usually I build Mercury's Treads for the Tenacity, but if you're against a team that AD is abundant, then it's better to use a Ninja Tabi.
Then The Black Cleaver helps at your attack speed, giving you the armor reduction at your target, combining with your Crushing Blow, it can really make some damage at your target.
The Madred's Bloodrazor is great against tanks like Alistar, Rammus and Amumu, but it's worth too against some carry-tankys like Jarvan, Renekton and Nasus.
The Bloodthirster is great late game, cause if you lose a lot of life in a battle, you can jungle, or kill minions for a fast regeneration instead of going back to heal.
And for the last item the Warmog's Armor, it's really great at the end, you'll have almost 4k HP and with your runes and his passive, you have a considerable armor and magic resist to not die with all this life.

At first I like to have the Crushing Blow for farming, it's great if you think you won't be able to kill the minion, or even get some damage at your enemy.
The sequence at a team fight is pretty basic. You first start with Nimbus Strike to get close to your target, you hit him once, then right next to your hit, you use the Crushing Blow for a armor reduction, if you already have the Black Cleaver, it gets even better, you get his armor really low, and you can cause a serious damage.
The ult I usually use just for some runner, he's running away from you, or from your team, you flash next to him, and ult him, he'll get up and get time enough for your team to blow him.
In a team fight he's good too, espeacilly for ults from Nunu, Anivia, Galio etc...

I go for 21 points at Defense, improving his suvivability at the whole game, and 9 points in Offense for Improved Exhaust, armor penetration, cooldown reduction and a little critical strike.

I like to have Exhaust for runners that are running from you or your team, and Flash for runners too and for you to run away from battles or from enemies, it's always good to have a Flash with you.
You can have Ignite instead of Exhaust for major damage.

He seems pretty squishy at first, but when you play some games with him, you get his spirit, he's very good at taking tanks and heavy carrys down, with his Crushing Blow and your Black Cleaver, you can take those down very fast.