OFF
Tracers won't help you aim, and turning them off doesn't help much either. If a guy doesn't see you coming, he doesn't have enough time to jink out of plane once he sees your tracers.
I love it when a guy HOs and then calls out on channel 1, "Hey, you got tracers off, don't ya?"
Duh?
To learn about lead: Find a squaddie that has a decent gunnery, and ask him to send you some films. Ignore his ACM and watch how much lead he uses on jinks, and breaks.