Is there some guide for weight lost and building muscle?

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I lost a ton of weight then stopped for a while (didn't gain any) now i want to finish what i started. Not only that but i want to learn martial arts, and be-able to do some flips, like gymnastics. First i would like to get in shape. Should i lose weight while lifting, or lose weight then lift? Is there some guide so i know i'm getting enough nutrients? Isn't there just certain stuff i can eat every day to assure i'm getting enough? I've tried Mypyramid and a million other sites, and it was all to complicated for me to follow. Help please