Diet is 80% as already stated. Training is breaking your body down and rebuilding it. How good you get depends on the materials you give your body to build with. If your a horticulturalist or agriculturalist and you want to grow magnificent plants or animals, all you worry about is what you feed them. Cock the food up, manky shitty plants and animals. People are exactly the same.
Before I busted my leg I walked 20km in rough country with a heavy pack, 20 days out of the month. And I had a gut, because I was eating shitty exploration camp food.
When I returned to my old fight gym my trainer had just finished all his personal trainer courses. He and I got into proper diet and careful body balancing gym work. Iv done it all before but Iv never taken diet seriously. After two months, people in the gym started asking him "what the fuck did you do to Tim". I still couldnt fully weight bear on on leg, but Iv never felt better. After three months, I had put on 11kg of muscle and I had better cardio.
I would read up on nutrition. Not the bullshit crazy diets, but proper results from proper research. Eating right is usually cheaper and tastier as well.