Depending on what jungler I'm playing, I will try to do a level 3 gank if I have healthy clears and am at least half life or above.
Though, yes sometimes there is nothing you can do if laners are just awful, but sometimes one solo kill doesn't mean that they will continue to die. It could just mean that they made one mistake or miscalculated damage. Still gank when you can, as getting kills on them will help fix the hole they put themselves in.
If the laner just keeps dying and dying and it's an ungankable lane (risking giving the enemy a double kill) try to camp a lane doing well and getting them so far ahead it won't matter that your midlaner is 0/5.
As for cheese stats you mean invading the jungle early to get a kill? You have to know your match up. Do you have some way to surprise them like a Vi Q into their camp? Is it a jungler that has a rough first clear?
I cheesed a Wukong as Vi and got first blood because Wukong's generally have awful clears unless the person is really good with him. Amumu is another that can be easily cheesed depending on your jungle pick.
If they losing lane but there's still hope of ganking, ask them to let the enemy push as far to the tower as possible then gank. Try to engage a second or two later after your laner does...any later and it could be death for them