Breath control has more to do with buoyancy control than with gas consumption. You want to use a regular breathing rhythm that is slightly slower than what you normally do on land -- more akin to the breathing of yoga or meditation. AND you don't want that breathing rhythm to vary, no matter what you are doing. This is not natural! New divers, when faced with any task, tend to hold their lungs full, which of course perturbs their buoyancy.
Gas consumption is far more related to efficiency in the water. Learning to be quiet and stable has a huge effect on how long your gas will last. Achieving horizontal trim, so that all your kicking propulsion is sending you forward (instead of upward) helps a lot. Slowing down, so you can enjoy the environment, is a huge component -- but is extremely dependent on being stable, so that you don't need constant kicking to maintain your position in the water.
Combine a regular breathing pattern with solid stability in the water, and you have an efficient, stable diver, and diving becomes much more fun!