Cho'Gath is a top/jungler personly i think he is better in the top lane he can either be an invunrable tank or something to output damage but what you might not know the tank version of cho'gath can actually do more damage not as ap though which is what his abilities except the ult scales in.

Cho'Gaths Q is easy to use but it can also be dodge so it is important that you think stategetly about placing it. It can be used in a compo with the other abilites to get close in range to hit them or to be able to hit your ult to get another stack

Cho'Gaths W is used mainly to silence enemies cause they won't shut up with there abilities it can also prevent them from trading and does a decent amount of damage so if you see them about to come at you wait till they are there w then u can damage them :)

Cho'Gaths E is used to help hit ranged targets or just to do damage or to farm remember if you perfare you can max this first instead of Q depending on your play style and it has lower mana so is sometimes better if you use your mana a lot

Cho'Gaths R Ult His ult is the main part of his kit it is used to do more damage and get more health you are able to do this 6 times on minions so i suggest right before you back you quickly feast on a minion so when you come back you can have it almost back up with an extra stack. Remember the more stacks you have the more heath and damage your ult does.