Actually...You'll want to learn to grow successfully, then learn to optimize your grow. In that order.

CO2 enrichment is rarely (if ever) done with dry ice or home brews, as it's costly and ineffecient. In a properly ventilated grow room, ambient CO2 levels are fine.

Plants don't have ears, but if looking to use your breath for additional CO2, try exercizing in the growroom. More effective, it's good for your health, and the neighbors won't complain.