14gas/14pool is hand down the best opener for most players under high masters.
Definitively the safest.
and react to his build, your zvz ratio will increase tenfolds.
If he hatch first, you can mass ALL lings once your pool finish's. In gold league, you should win with that in it self.
As you rank up, you're gunna need to add drones in while you're making lings and expo during pressure and minerals become available, as higher level players will be able to break even with your build with hatch first. Also, certain maps(wide-open natural) it's actually almost impossible to hold it off.