Half Bad Trilogy Series 3 Books Collection Set by Sally Green:

Half Bad: He's half White Witch, half Black Witch. His mother was a healer, his father is a killer. He's been kept in a cage since he was fourteen. But if White Witches are good and Black Witches are evil, what happens if you are both?

Half Wild: After finally meeting his elusive father, Marcus, and receiving the three gifts that confirm him as a full adult witch, Nathan is still on the run. He needs to find his friend Gabriel and rescue Annalise, now a prisoner of the powerful Black witch Mercury. Most of all he needs to learn how to control his Gift - a strange, wild new power that threatens to overwhelm him.

Half Lost: Nathan Byrn is running again. The Alliance of Free Witches has been all but destroyed. Scattered and demoralized, constantly pursued by the Council's Hunters, only a bold new strategy can save the rebels from total defeat. They need the missing half of Gabriel's amulet - an ancient artifact with the power to render its bearer invincible in battle.