Coming from a teenager as well...
Heres a tip, if you are doing a three day split with cardio in the off days, perform your nutrition routine like this:
Morning: Wake up, drink water, 15 minute high intencity cardio (85% and higher)
Post Cardio: Whey Protein Isolate (of whatever variation) at 15 grams, dextrose or maltodextrine at 20 grams. Glutamine at 5 grams. Might wanna throw in some NAC, but be sure to include vitamin supplements like vitamin C, and B Complex.
Rest of the day: Low GI carbohydrates, and generally healthy, unrefined foods. Include protein shakes to supplement your protein intake. But do not take whey protein alone without any other proteins, as a meal. Take it to boost anabolic activity and blood aminoacidemia levels around meals that contain protein sources (like chicken breast for example). If you want to supplement with a protein supplement to increase your protein intake, find a protein blend. Casein/Whey/EggAlbumen/Soy would be useful. Be sure to include carbs and fat. For fat sources, stick to healthy oils, and stay away from saturated fats. Supplement with flax oil, and add olive oil.
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On the workout days (if you work out any time but the early morning), this is how it should go.
Wake up: High GI carb, whey protein.
30-45 Minutes later until pre workout : low GI carbs, slower digesting protein sources, healthy fat sources.
Pre workout: load up on some low GI carbs about an hour before. Take a pre workout shake of 15 grams of whey, and 35 grams of dextrose or maltodextrine. Midway through the workout, take another shake similar. Do not include milk in these shakes. Post workout, throw in some micellular casein, and a little more maltodextrine to keep the insulin spiked. Once the aminoacidemia levels in the blood start dipping from the whey, the casein should have kicked in.
An hour after the workout: Low GI carbs, and slower digesting protein sources. Include healthy fat sources.
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Before bed for both days, include some milk with a protein blend. I prefer to get another shake ready for the middle of the night before I go to bed, set my alarm, wake up, drink it, and fall back asleep. The whole process takes less than a minute.
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