As a short introduction, Yorick is a strong 3v1 champ at 2+ items. He can at most 3v1 and nothing more. Always keep that in mind. He is not your flashy outplay champ like Yasuo, or OP burst top laner like a fed Riven. You can 5v1 IF your opponent will 3v1 then 2v1 then you can but not 5 at the same time.
I have 350k mastery with Yorick but I only played him a lot recently although he is kind of my secret main. Yorick is a 1v1 monster at level 6. If you wouldn't die during laning phase, at level 6 you outpower ANYONE in the game (except for Jax and Irelia which I would explain later).
With all of that out of the way, I would let you in with a specific gameplan of how I play Yorick in Patch 9.5. I have a different gameplan, strategy, runes, and items on Yorick so I suggest trying this on Normal/Casual game first.
Pick/Ban:
ALWAYS ban Jax. No questions. His kit LITERALLY counters your whole kit. His E, the block thing, blocks your Q, maiden auto, and ghouls for the duration. You cannot outpower him since your main damage is on your ghouls. His jump outmanuevers you and counters your W. If he kills your ultimate first before dealing with you, you're basically dead. If you are not dead, you will be out of commission for the whole 2 minutes (maiden cd is 120 sec at lvl 6). so ALWAYS ban him. I don't have a gameplan with him rather than banning him. I know, I tried, nothing works.
Your worst matchups will be:
Irelia:
Her Q destroys your ghouls. 1 Q = 1 Ghoul and the sad thing is that it resets after killing minions (or pets). Your only chance is if the Irelia is not a main and misses her E at level 6 OR fights you without killing all of your ghouls first. If you're dealing with Irelia mains, you build pure tank (I would describe below) and ask your jungler to camp you. Learn to cs under tower and split push mid-late game with wards. Never 1v1 her during mid or late unless you are super fed (at least 4/0) from jungle ganks.
Tanks:
This includes all tanks BUT the worst will be a good Nasus player since he can stack with your ghouls. Against Nasus, you freeze lane without summoning ghouls. At level 6, if you cannot kill him, hard shove lane then roam. If you're a smite top push wave > invade jungle > push wave > take YOUR Krugs/Gromp > push wave > recall. If you're not taking smite, ask for jungle gank.
For other tanks, If you cannot kill them, play as normal. This is mostly free lane BUT you won't snowball as much unless you are taking Kleptomancy Runepage.
Item set:
Start with Corrupting Potion (normal) or Doran's shield (for poke like ranged top, champs with dot like darius or teemo, and early game burst like riven, although I take corrupting with Riven since I am used to playing against her).
First back will be a corrupting potion and boots if you started with doran's shield, Sheen +boots if you started with corrupting, executioner's calling+boots for lanes with heavy sustain like Chogath, Mundo or Nasus.
Full build by order:
Trinity Force > tabi or mercurial boots > Death Dance > Visage > 2 tank items (depending on matchup).
Use the above if you're on normal lanes. Death Dance is important if you're using a smite top summoner spell for Solo Baron at 20 minutes.
Against hard matchups, I usually go full tank.
Runes:
Grasp with Demolisher for most match ups.
Kleptomancy for lane with low kill pressure early or Tank match ups. This would allow you to reach your mid game earlier. If you're using Klepto rune, at level 1, use auto for last hits, Q on enemy champs to proc the Kleptomancy. At level 2+, E on opponent, if hit, Auto>Q for 2 procs of klepto (your Q resets auto).
Summoner Spell:
Teleport:
If you're versed on TP ganks, and against hard matchups for roaming.
Ignite:
If you're much comfortable. This makes you immensely strong early.
Smite(My personal choice MOST of the game):
Yes. Top smite and I am not trolling. This is important: Make sure to tell your team that you are not trolling and you need this for 20 minute baron during champ select. This would allow your team to not troll.
Patch 9.5, Yorick Ult has been nerfed with his Ult damage decreased and % health damage decreased. This does not affect his early game BUT this affects him during solo Baron. Without Smite, you cannot do Solo Baron 20+ minutes. I know, I tried.
Last and Important Notes:
#1 Yorick can carry IF your team would listen to you. He can carry by split pushing and not by team fight. Your opponent needs to send you 3 people to have a chance of killing you at 2 items. Take note: "have a chance", 3 people is not sure yet. Your team can then 4v2 while you are 1v3. If you're team cannot kill 2 people, they should quit lol.
#2 Do not fight without your ultimate. You are one of the strongest with your ultimate. You are one of the weakest without it. TH during laning and play safe if your ultimate is down.
#3 Approach velocity in inspiration can make you reach any opponent who used their flash.
#4 Trinity Force + Deathdance + 2 stacks of smite is required for Solo Baron at 20+ minutes. If your team is feeding, make sure THEY DO NOT HELP during your Baron in 20 minutes. If your team goes to Baron while you are doing it, your opponent's team would as well and chance of succeeding of getting baron gets lower.
#5 My normal trading in lane and during teamfight is to have 4 ghouls (with ultimate if possible), E > W on opponent then Q them to death. If you think you can't kill, don't over extend. You will kill them eventually.
#6 THE MOST IMPORTANT: Please leave comment if you have questions (lol). Detailing everything by text is hard. I might have missed some so a feedback is appreciated.