I've gotten back into LoL, and I'm enjoying myself. I always enjoyed Cho Gath, but I've noticed its either a huge hit or a big miss. I was in bottom lane with Teemo vs Miss Fortune and Sona, and we got obliterated.

However next round bottom vs Master Yii and Varus, me and a Taric destroyed them easily everytime with few scratches.

What I'm trying to ask is

1) What is a good order for Cho Gath's abilities? I usually start with Vorpal or rupture.

2) Is there a certain type of enemy that he'll do better against?

3) I usually follow the recommended items. Should I deviate from that?

Finally if there's anyone who's experienced with Cho Gath I'd be thrilled to get some real time help and pointers.

Thanks!