This is a build i have come up with myself, i do very good with this. hope you can too.
:)

I focus on stacking attack damage and some health, read on to know more

You take solid Attack damage, crit and speed. like shown ^^

Most points in strong offense, a few leftover points in armor and mana. Because thats good at the start of a game.

I try to max out omen of famine first, and taking pestilence along the way. omen of war i max last of all spells.

This is good because say you are hiding in a brush at start and you are level 2 or so, an enemy walks by to kill minions. you jump out and hit him with pestilence and famine. he gets low hp from that. farm minons until 5. await your enemy. Pestilence, famine, war and just chase and he is either almost dead or dead, depending on the enemy champion.

And about the ulti, i rarely use it. unless its a teamfight or i need some extra damage for something

Look at the items i listed, i take these because i want a strong damage output and high hp, i buy spirit visage to get cooldown reduction and to get more healing from Famine. this is great.

The other items i take like i said for damage and health.

Also, you dont have to buy the Resist boots, tab and check if there are many magic dealers in the enemy team, if there are u take them, if not, go with attack speed or just move speed.

Flash and heal, two best spells you can have in my opinion. If someone tags you with ignite or you get low hp (which you shouldnt), just heal. someone tries to escape, flash up to them.

about to get ganked 3-5v1? flash over a wall.

If you want you can jungle with this build, hit a pack with pestilence. smack em abit. heal with Famine if you lose some hp. Basic stuff.

Well that sums it up i think. Follow this and you should play yorick like a beast.
Feel free to Contact me with any thoughts if you find something you think can be improved or alike.

Have fun, Yorick style.

Credits for this Build goes to me.
Summoner name: Engobbaz
Realm: EU nordic & East