Well the other day I was playing NS and got the idea of staying gorge the whole day, I got more than a hundred gorge spit/healspray kills combined and built who knows how many WoL's, what I found was useful over any other upgrades was SILENCE!
When a marine hears a gorge waddling around he tries to kill it cause it is so vulnerable, it can't attack (usually) from a range that a LMG can beat, so what I find is wait in ambush as a gorge and spit from behind and don't miss, he won't hear it but just think its a silence skulk or something, if you miss and he sees a gorge spit going past him he will turn around and kill you.
I don't know if anyone else has any better tips for gorging and still being able to kill, add to this topic freely