I remember reading this years ago, so sorry for any confusion or possible spoilers. In this manga's universe there were people (I don't believe it was everyone) that would develop special powers that had different conditions. They could be like "I can shrink any person to put inside of any box I hold" or "I have the most powerful punch." The manga followed a teen /young adult girl whose power was "as long as I believe I can do it, I can do it." I feel like she had red hair, but that might be a red herring (sorry for the pun). If I'm remembering correctly, she originated on an island that had massive trees/tree houses and then took a boat to the place where other people with powers lived/worked.

Esprit most likely...

~4400 manga completed
~1700 ongoing...

Yes, that's it! Thank you!