Disclaimer: This is very much an off meta pick and intended for fun in normal game. Yes this build is weaker than the lethality or classic build. However it is still fun to play.

With this out of the way, the goal of this build is to maximise the annoyance potential of Yorick's kit, to make I believe one of the most frustrating champions to play against. Fun right?
Your whole purpose is to unleash waves of DoT indusing, slowing ghouls, while you remain forever out of range. If you want to go in, like fair fights and skill, I’m sorry this is not for you. We are here to play PVE, macro and remain away from action.

Who am I?
Just your average Yorick OTP. No I’m not challenger and neither are you, this guide is simply here to showcase a way to have normal fun in normal games abusing other average players' fun.

You are a Mage, a Caster, a Necromancer. You wouldn’t expect Azir to dive in enemies, and the same applies to AP Yorick. You do not have the melee damage or sustain of any other iteration of Yorick, so really you do not want to reach close range.
In laning phase, you can safely poke with E + Comet, or if you are really facing a dangerous laner, farm with E. It is not a problem to miss CS for the first three levels. Better healthy with no CS than dead with three. You will have plenty of opportunities to get more later. Once you get your Q, try to send E+four ghouls at your enemy as often as possible.
Your real game starts at level 6. Summon your Maiden, let her spawn four ghouls, throw them at your opponent. You can make any other champion wait under their turret taking waves of ghouls. Don’t go in yourself unless you’ve poked them enough and you can assure a kill with ignite. Try to stay away so that you can safely avoid ganks.
The “classical” option would be to start with Serylda first item in order to make your ghouls sticky and have a minimum of AD yourself, then complete Liandry. This is perfectly viable. However you can also start with Liandry and then opt for Serylda (better) or Rylai (cheaper).

This starts as soon as you get your Maiden and you keep your laner under their turret.
You can easily make raptors with your maiden spawning ghouls. Shove the lane, send ghouls on your laner, go away to either get a camp, harass the enemy jungler or help yours.
Get gold wherever possible: scuttle, heralds, enemy and ally sides camps. Your laner should always be under turret and unable to move as quickly as you.
Try to always move around with ghouls: Those from the wave are sent to your laner (you send the first four with an E, and then keep spawning them as they get killed). Those from the camps stay with you or are sent to the jungler.

In Mid game, try to get a side lane and apply pressure. You want to attract someone, send them ghouls and leave. If they can catch you, play with the fog of war instead: be there for two waves, leave in the jungle, go back when the lane gets pushed to you or they leave. Be everpresent and everannoying. In bigger fights, stay away and send Es. Going in would mean your death and the death of your pets, therefore no damage. Your spells and pets perma slow, so your cage is better used in defense, where you can protect your carries as well as yourself. Your role is to always have four ghouls dealing dots and slow: fight near a lane, near a camp, use enemies’ graves. You deal a ton of % health damage (E, R, Liandry, Demonic) so you are really effective against tanks. Against carries you are sticky and help pin them down, but you will often lack damage to kill them yourself. Again, survive. You are more useful sending ghouls and leaving the fight immediately than dead because you stay too close to the sun. You might get flamed for “not participating” but that’s just them not understanding your champion. You can even let the maiden fight with your team by releasing her on a lane with them while you push elsewhere. Leaving the maiden alone on a lane is not as efficient as AD Yorick, because your ghouls lack the damage against minions, but it is a very good distraction while you may help on an objective.

You completely fall off in late game. Still annoying but not a threat anymore. If you haven't won the game by now, it will be harder. Try to catch people off guard with your team, send ghouls to prevent opponents to join so you fight at an advantage, push lanes to secure objectives, aggro enemies to secure objectives. Never get yourself caught by staying far away.