This is my first build post, I have for about a month, been playing cho'gath as my main champion, so I think I know what I am talking about. All that time, I have been lookign for a full tank build, with no AP, and have never seen one that didn't incorporate rod of ages and rylai's crystal scepter. So here I am showing you the build that I have refined, I hope it is helpful.
Cho'gath's passive, Carnivore, allows him to sustain, he can just get last hits to regain health and mana, this means that he will probably be on full health after clearing a few waves of minions, therefore he can stay in lane and have a level advantage and mana advantage on his laning partner(s), even greater if they do not have a solo laner.
Rupture allows Cho'gath to knock up and slow enemies in a circle, it has an initial delay, but if you can successfully hit with this, it is a very good opener to a team fight, or a good way of catching up to an enemy to finish them off. Also when running away, it can be used as a chasebreaker.
Feral Scream damages and silences all enemies in a cone, this allows him to evade abilities and be very effective and mages. Along with magic resist, he should be pretty un-touchable against champions such as ryze, brand and xerath.
Vorpal Spikes damage all enemies in front of Cho'gath, this is a very effective farming tool, as it can clear out a creep wave in one hit, if they are all damaged already. However, using it while attacking a turret does not inflict any more damage to the turretand the tower will attack you if a spike hits an enemy champion behind the turret.
Feast inflicts a large amount of true damage to an enemy, it is 1000 on minions, always, but ability power will affect its damage on champions. I Cho'gath kills a minion, monster or champion with Feast, he will gain a Feast Stack, increasing his size and health. Grinding this on minions every cooldown is a very effective sustain, its cap is a 6 Feast Stacks. Afterwards you can use it to harrass an enemy or kill someone very easily in a team fight.
Getting Regrowth Pendant allows you to easily recover from any engagement with the enemy, a good sustain early game to give you the level advantage and item advantage, along with carnivore, it should allow you to win any early game engagements as you will have the health advantage. Rupture early allows any ganks to instantly be stopped, it is a useful way of preventing a CC effect happening, removing your chances of survival.
Getting Vorpal Spikes early should allow you to harras the enemy, as long as they are behind the minion you are attacking. This can also bring you double minion kills in one hit, which is great for regaining health and mana with Carnivore
Levelling up Feral Scream a lot early gives you a good harrass, as rupture then feral scream combo will do a large chunk of damage and the mana can be regenerated using carnivore.
Philosipher's stone gives lots of gold. :D Mercury Tread's is really useful for getting out of CC abilities quickly. :D Heart of Gold gives lots of gold. :D However, converting gold per 5 abilities early will remove the gold per 5, so do it later.
Rupture is not for damage, so it is better to level up Vorpal Spikes after Feral Scream for maximum creep score and health and man regen.
Constant Harrassing will keep you on low mana, even with carnivore, so when it goes to mid game and bigger engagements are happening, you need to be there. As a tank, you must absorb all the enemies abilities, allowing you ad carry and mage to inflicy maximum damage on the enemy. If your team is a fail, you will die, instantly, and your team will run away, hope that this does not happen. If they flame you, don't worry, you were doing your job.
Dying means losing feast stacks, but luckily, you should be able to get them back in the jungle, or just by grinding minions.
Generally, if you have not died by now, you are either:
Someone who does not trust their ability to stay in lane below 40% health, so you will be under-levelled.
or, someone who is an absolute tank and needs to be on the challenger circuit.
or, you have been laning against a complete noob who stays out of lane all the time and their jungler never cam to gank you.
Please be one of the last 2, trust yourself to sustain in a lane, it is theon ly way to win as Cho'gath.
You will not have got many kills, you should always go for the assists, get as many assists as possible to stack up the gold as well as laning, kills are for ad carries and mages, not for supports and tanks, be happy with 6/5/25, 7/2/38, 2/5/64, that kind of thing.k/d doesn't matter, d/a does.
At level 11, you should be aiming to have built force of nature, it should be around the 25 minute mark and you should be transitioning into mid-game, team fights will happen, you will likely win them with force of nature and 4-6 feast stacks. Don't panic if your team abandon you, use flash to escape any more CC andget behind a turret, if you die, flame your team, call them noobs, ask for the other team to report them, whatever, just as long as you get the message across that you hate your team for leaving you to die.
Once you have built Frozen Heart, you will be unstoppable, any attempt to kill you will be destroyed, as you will have the speed to run away, and the health to remain alive. Just focus on targeting the squishy damage dealer with you abilites, take him/her down before they do serious damage to you team, then focus the mage, they probably have AoE abilities, so you team will have been attacked by them, try to make them target you while your team flank and kill them and the rest of their team.
During mid-game, you should take dragon, and should be pushing towers after winning team-fights, do nottake baron until you have pushed to their inhibitor, and they are nowhere near/dead, because baron can easily be stolen from you by a very well timed ranged attack form a mage, or a dive-bomb by an ad carry.
Do not push on your own, always as 3 or more, take dragon as much as possible, deny the other team baron or dragon, take their buffs. Take down remaining towers and destroy inhibitors, generally, if an inhibitor goes down, it is the end of the game, because of surrender, or large numbers or superminions destroying the nexus turrets.
If it is not over by now, you should have finished your build, Guardian Angel will save you, it requires skill to escape after revival, usually, use ruture and feral scream, maybe kill someone with feast, but do not take them all on, expecting your team to join in, if you go down, don't give up, at least kill someone. Sherelia's Reverie will give you team a speed boost, which is useful when running away or chasing the enemy. Randuin's Omen is great in team fights and negates the ad champs with the attack speed debuff. So if you are using it, focus the mage the the others, as they will do the most damage. If nobody has won by this point, then just keep pushing and pushing, and maybe after 2 hours, someone will leave or surrender vote and the game will end. However, this is unlikely to happen, I have never finished this build.
Cho'gath requires skill. He is difficult to play and it pays to stay alive, my best score with a similar build was 11/6/28, this is what you should be aiming for, and should beat, if you are skillful enough. Please tell me if this build works for you, I spent an hour putting this together, I just want feedback, it works for me, so it may work for you.