The Law of Devil's Land - Anthony J. Viola - Bog

Seventeen-year-old Ghonna "Gyle" is an outcast unsure of their identity, trying to get by in a post-apocalyptic society where traditional values reign. To raise themself out of the Lower Ranks, Ghonna participates in the annual Imperial Events (a cross between the Olympics, X-games, and Roman Gladiator Combat).
With each stage, the stakes increase, the competition is fiercer, and the possibility of death becomes likely.
However, Ghonna uses their ingenuity and guile to methodically progress through the Events, and a "once-viewed pariah of humanity" wins over the masses, evolving into a messiah for a secret reform movement.