Most kids your age will not take this advice, but by far your best bet, both short term and long term, is to just focus on the following:
In the gym:
-Cultivating lifting technique on a few big lifts: squat, deadlift, bench, military, pullups, rows, curls...probably all you need plus some ab work, and some modest assistance work where you feel like you need it.
-Focusing on load progression over time. You must add weight to the bar.
-Not doing too much too fast. 3-4 days a week, focusing on big lifts, keeping your volume under control, and keeping it basic.
In the kitchen:
-Develop sound eating habits by eating whole foods. Beef, chicken, fish, vegetables, berries, nuts. That should be most of your diet. Eat as much of these foods as you want/can. Don't eat shit and you should lean out if you are working hard in the gym.
-Focus on getting a good meal in shortly after you wake up, and being fed before/after training (with something you can stomache). The rest is much less important.
Just do this. Don't make it more complicated than it needs to be.