[@The_written_John] From what I've seen, semblences are reflections of who you are as a person. Ruby and Nora are both pretty hyper, fast paced characters; Ruby has super speed, Nora gets a power boost from electricity. Yang is an adrenaline junkie who loves fighting; she gets a power boost from taking a beating. Weiss appears to share her glyphs with her sister Winter, possibly symbolic of her dedication to her family's honour. Blake confessed that she spent much of her life running from problems, and so her semblance creates a clone to distract and intercept blows. My Cyra endures every form of abuse that is thrown at her, and is frequently too frightened to create positive change for herself; she becomes like a mountain standing against a storm, immovable. 

Think about your character's traits, both his strengths and his flaws as a person. Create a power that represents the sum of those traits.