I've seen trinity jump buildings with her legs waving in the air. Is it a myth that if you do this you jump longer distances or it helps propel you through the air?

Absolutely NOTHING about any of the matrix movies has any bearing in reality.

maybe so, but i would love for mythbusters to try an,d doge a built, like Neo did all the time

Waving with your legs helps you propel as much as flapping with your hands while free falling...
Our bodies just aren't built for that kind of acrobatics. We are too heavy, our bone structure is wrong and our limbs are not able to generate any real force against air. That's why birds can fly, but you can't.

Don't people learn anything about anatomy and physics nowadays? Or has the inholy church of eternal stupidity taken completely over?