you can choose two ways of jungling with cho' gath

way 1: start at wolfes and after wolfes go directly to blue.
when you finished your blue and your the blue team, gank either top or mid, if you are the purple team gank either bot or mid.
after this you directly head to wraithes, red, and the small golems.

way 2: you start at blue, then you go to wolfes, after that head to wraithes.
now you can choose 2 things, either you gank mid or you take red/small golems and gank top
this is your own choise and this can also depend on the situation.

Cho' gath is a melee ap/tank
cho' gaths pasive gives him the ability too have a lot of sustain in the jungle.
you'll have more health then the average other junglers after jungling, this means you can more easily gank lanes (with more health) or just go on with your jungle.
cho' gath is in early game a damage dealing monster so make use of it by ganking a lot.

in the mid stage of the game you want to focus on clearing wards, counterjungling the enemy jungler, and keeping as much pressure to the enemy team as possible

in the later stage of the game you need to be the tank in teamfights, your job is to stand in front of everybody, normally you shouldn't be too afraid of being poked down, if you have full stacks on your ult and you have a warmog's armor you should be able to regain all that health.
an important thing is too always stay where your teammates are, you are the most important front liner of the team (most of the time).
also you are the one too decide if you go all in or not and back away.