This is my S4 build for yorick and i hope you will like it and you will use it in your games.
When you play yorick you have to be carefull at your mana, because if you spam the skills you will lose it immediatly.

I choosed warding totem because is the most usefull at the begining of the game, but you can choose what you want. My opinion is that the sorying orb(blue trinket) is only for support.
It depend on your playstyle.

I choosed trinity instead of iceborn gauntlet because it have more stats and it have very nice proc with Q.You can choose gauntlet for slow if you think your enemy is vulnerable to crowd control.

Flash is very good on yorick because he dont have any escape,only his Q but you can be exahusted and slowed too, so i think flash is the best choose.
Ignite is good too, and you all know what ignite is used for.
You can choose teleport too, if you're against shen or if you like it more.

Pros:

- A decent farmer/pusher.
- The best top sustain in the game in my opinion.
- Ultimate can be used on teammates, usually on adc.
- Is very tanky and have big damage with the gouls.
- Great harass at early/mid game.

Cons:

- He is using very much mana, untill you build tear of the goddess.
- No escape abilities,only flash.
- Omen of pestilance is scaling on AP so it don't have so much dmg like the other skills, so you hamve to max it last.
- Ultimate can be wasted if you don't use it at the right moment.

The masteries i selected are very helpful if you play with this champ. If you guys decide if I forgot something tell me. This is my first build and i don't know if i did good, but i hope i helped. Good luck in ranked and have fun.