This may be stupidly obvious, but when facing Yorick as Nunu
 

Do I eat the creep wave or his minions?
What do I max and build first?
¯\(°_o)/¯

Creep, I would assume, he poops out minions like nobody's business - so you can at least run one of them out...

Tho, not really a nunu player, so maybe not? xP

As a yorick player, I'd advise you to eat the creep wave. I can poop out minions like no tomorrow, and eating one won't really make a difference. Eating the creeps will at least push the lane a bit in your favor however.

As a bit of advice, smack the red minion, run from the rest. The red one heals yorick, no real point in killing the other one's as you'd just be tanking their damage and yorick will slowly whittle down your health if you let them hit you.

Also, the red minions are his only sustain mechanism, so if you draw it off the creep wave (they prioritize champions) and kite it or kill it, he won't be getting health back.

As for what to level first, don't play nunu, can't really advise you on that.

R/G colourblind, I can't tell the red and green minions apart. Heh.

Hmm, if it's not moving abnormally fast and it doesn't have flies coming out of it constantly it's the red one. If you saw him spawn it at range and no flies, it's the red one. Only ways I know to tell without the color code.

His ghouls all look the same to me. I hate every single one of them.

But yeah either kite the red ghoul and eat the minion wave, or eat the red ghoul and ice blast/eat the minion wave if you have CDR. You'll outsustain him unless he gets a sanguine (and if he does, then just keep iceballing him and eating stuff).

Ghouls die in 5 seconds regardless of what you do, and have 35% of Yorick's max HP when spawned. Does that help you answer it?

IMO, eat a real minion, and just run away from the E ghoul so you don't give him extra healing. If you don't, I imagine a large minion wave sitting on top of you right outside the point... I may be wrong, but I wouldn't want my true damage nuke to go on a fake minion that lasts 5 seconds and has on average just over 2 seconds of CD (excluding CDR) at max rank (all 3 basic ghouls. Obviously each one individually has a seperate longer CD, but if you consider ghouls/second it works out to ~1/2) when I could instead chunk down something that will actually be banging on my turret door if I don't kill it.

As far as builds, I have no idea. I would probably just build standard infeed nunu stuff and hope it works out. I would guess chalice start with eventual frozen heart and probably gunblade starting with the revolver while maxing R > Q > E > W, but I haven't really run the numbers on which skilling order is better for which types of nunu matchups, so they are 100% guesswork.

Eating ghouls is absolutely pointless. Don't do it.

The exception is when you're trying to kill him, then try to eat the red ghoul. If you do not, he will outsustain your damage with that alone.

Also if you notice he's out of mana you might want to eat a few since he's not able to spam them. Just make sure he's slowed all the time so you can get to the health relic first.

doesnt the green also have this ooze bomb when he spawns? and the red doesnt
as the greens aoe and the red isnt?

Eating minions will also give you actual GOLD and help counter-push the lane. So definitely chomp down on the actual minions instead of his short lived ghouls.