diet.?

so im 15. 230lbs. 6ft. i recently lose 20lbs. i was 250.

now i exercise enough. active and play sports everyday. go to the gym. but the one thing missing is a diet. what should i eat in a day. like what type of foods to eat or not to eat?

i usually eat breakfast. some cereal or something. and lunch chicken or something like that. dont really eat vegetable or fruits. my trainer said that what i eat isnt at all a good diet, and i aint losing weight with just excersize alone.