160 on hit damage when devourer is done, and then hydra just scales off of ult and the hp items. With the current meta as it is there's really no point stacking up resistances if you can have hp and do damage, so Wit's End and Ninja Tabi are enough considering Sterak's.
Having about 4000 hp with more or less 100 of each resistance is enough in my opinion. Sterak's, of course, can boost your effective hp to around 5500.
With this build you will have a surprisingly large burst in terms of hybridized raw damage. After smiting, if you land your q and w with an autoattack you're almost guaranteed to get in at least 2000 damage with Titanic Hydra's active and your ultimate. (305(q)+275(w)+80(w)+60(devourer)+~40(hydra passive)+~450(hydra active)+40(wit's end)+675(r)+147(base ad+runes/masteries(actually more like 140 but this adds to a nicer number ok)+123(item ad)+164(chilling smite)=1520 raw mixed damage + 839 true damage at level 18)
Assuming you can land more than one autoattack during that time (which you probably should) you are basically doing full AP level damage as each autoattack will be hitting around 500 damage total (270+80+60+40+40=510).

Just max e and hit them a lot until you can eat them. Do try to keep ult at 4+ stacks. Your q and w are there to help you hit more autoattacks.
Keep in mind enemies can't flash when they're silenced, so if you land your q try to get the w off before they're back on the ground (you know, so you can hit them with more autoattacks).
Chilling smite also practically guarantees hitting your q if the target has no dashes or flash (which incidentally, a smite for a flash is definitely worth it).

Could go more offensive but damage reduction for you and your team is always nice, especially considering how often your laner risks their life when you're ganking for a losing lane.
You could take oppressor instead of bounty hunter depending on how confident you are in your ability to kill at least 3 different enemies.
Honestly I'm not sure about most of the masteries that much I mean you could take lifesteal/spellvamp for more sustain since you do a lot of damage to jungle creeps.
Explorer would be nice if you didn't have 4000 hp and would get like 160 hp from Veteran's Scars.
Strength of the Ages would be nice too considering you can get hp.
And so on, so if you don't trust me on this do your own it'll probably be better in one aspect if not all.

Pretty standard for a jungler I mean you could take more attackspeed (clear jungle faster) or more attack damage (more damage on hit for ganks since you usually don't get to stand still and attack) in your Marks, depending on your personal preference
Movespeed Quints are just helpful in general early game but you can swap them out too.
Seals and Glyphs are self-explanatory.

Killing jungle creeps efficiently isn't really that hard if you're Cho'Gath, you can clear starting from either side of the map depending on how you want to set up your early game ganks.
Really most of gameplay differs so much every game that I don't want to get into detail for that in explanation.
But once you hit 6 ganks should be relatively easy, try to target people without dashes since a smite into q will at the very least force a flash if not a guaranteed kill.
Don't forget to stack Devourer since that's kinda important (it should be done before 25 minutes unless you're really reeling in the gank money).