Just one coat. Then use a good quality paint to cover the wall surface.
__________________ Ren: Now listen, Cadet. I've got a job for you. See this button? Ren: Don't touch it! It's the History Eraser button, you fool! Stimpy: So what'll happen? Ren: That's just it. We don't know. Maybe something bad, maybe something good. I guess we'll never know, 'cause you're going to guard it. You won't touch it, will you?
Don't use KILZ on new drywall. Use a quality drywall primer from Sherwin-Williams or Benjamin Moore. They make latex based primers that are much more effective than KILZ. KILZ dries too fast to adequately soak into the joints.