This is my first Guide, so please dont hate me ;D.
I only want to say a few words to the item-build.

The Cloth armor:
I think its better to take the armor than boots or dorans blade for the start because you will get lower damage from monsters. So you can gank better because you leave the jungle with more life and you will get lower dmg from champion, what is avoiding a fail-gank.

Starting:
I start at the wolfes. You can do them alone because of your passive, but when you get help from your team you will have 3 healing pots left after blue instead of 2. Then i gank top/ bot, because at this time there will be no ward.

Boots/ Madred's:
When you finished the gank go to the other side of the jungle and port back or gank and port back. Now you should be able to purchase the boots or Madred's. Both will let you jungle faster but the boots are better to gank.

Berserker boots:
I always use them because you need fast attack speed for Wit's End.

Glacial:
Every tanky champion needs armor and as warwick mana is always good. When u got this item you will never need the blue and can give it to the ap carry.

Phage:
Life and attack dmg, indispensable against summonors which think they can win in 1v1 (for example the enemy jungler).

Frozen Heart:
Just start the teamfight with your ult on the ad carry of the enemy team and support your team with this item!

Frozen Mallet:
More deadly than Phage. one Hit and there is no way out for your enemy.

Wit's End:
For your ap resist and also offensive boost.

Madred's Bloodrazor:
With this build yoou got not high ad so prozentual dmg and atack speed is nice.

Sunfire Cape:
With this item or Tiamat you can just jump in the enemys with your ult and deal dmg to all.

The only thing i want to add is that you should not use flash to gank... think about this scenario:
u r waiting to gank mid. u use flash to go in, then ulti. at this moment 2 enemys come from the other side of the bush. your mid champ will run for his life and you are now in a 3v1 without flash... thats bad ;D

I hope my english is good enough that you all can understand :D.
As i said this is my first guide but it is still good for beginners.

P.S. i dont want to say anything to the ad build because i play like the first build but the 2nd build is the way i play when the enemy team is really weak.