I need a good diet and exercise plan for teenagers. Or some program.?

I see people recommend buying vitamins and drinking tea and all this stuff. But my parents are rarely home so I have no one to take me to buy that stuff! My grandma usually cooks and she always makes fattening food. So I need an alternative. Heres my moms mentality. Exercise and you’ll lose weight. But I know that exercising is only part of losing weight. Diet is more important! Well I need alternatives! Healthiest thing I could probably get my parents to buy is salad. . . Can’t eat cereal for breakfast cause I’m lactose intolerant and I don’t want gas while I’m in school!
I’m 14 5′11″ 220 pounds. Please help! I’m even willing to pick fat camp for an option. I’ve got a big build. Worked out for about half a year when I was 13 years old, don’t know if that’ll help.
And sorry for the long details XD.