Hello this is a semi guide but mostly a build. Like most ppl i bought Yorick and was like HOW DO YOU PLAY THIS GUY?? but I will answer your questions and solve the malignant mana problem of Yorick.

Mana Regen is the most important, so Mana Regen/5 Per Level Glyphs and Seals would be optimal.
Armor Pen Marks and Quintessences are also helpful due to him using AD only, as he is one of the few champions that does not benefit from AP at all.

Yorick is like a DPS but requires CDR and mp5 like a support or a caster kinda weird ik but i digress it works. Get the standard 9-0-21 Build, as Yorick doesn't need Defense Masteries and Utility will provide vital for his Health and Mana Regen.

Pros
Great damage
Possibly a carry
Strong in team fights
Amazing at laning due to maxed E so he wont have to leave until you want to
High AD with little mana problems after the Manamune is bought
Cons
Not too great in 1v1s
Can be focused down

Yorick is the most team work dependent dps in the game. For ganks keep walking in and out of the fight and use your E to heal then re enter the gank. the reason is that people will focus you down as a dps so you need to interrupt the damage that they deal and have them focus on the tank for a bit. but when u use your E then W re enter the gank for maximum survive ability and damage

For farming you should focus on last hitting but the skill to last hit would be to use your E when you are weak... but when you are not weak, use auto attacks to last hit and use your E to harass but watch your mana. When farming for example if you gain about 20 Mana Regen per 5 and the cost is about 50 then wait about 10 seconds to use your E again. this is why Mana per 5 is so needed. the more Regen, the more often you can spam without losing more mp than you are regenerating.
Use your W to AOE last hit or to push the minion waves.