Familia Gladiatoria is a set of free wargames rules for gladiator campaigns.
gladiator
Glory In The Arena Gladiator Rules
Glory In The Arena is a set of rules for playing gladiatorial combat with 54mm figures.
Habet, Hoc Habet! Gladiator Rules
For a limited time, the Habet, Hoc Habet! Rules from Scale Creep Miniatures is available on a pay-what-you-want basis. These are designed for fast combat among Roman Gladiators, including campaign and gambling rules.
Roar of the Crowd Gladiator Rules
Roar of the Crowd is a set of free rules for playing science fiction, fantasy or historical gladiator games.
Spartacus Gladiator Rules
Andy Watkins has one page set of rules for games involving Roman gladiators. You can use the fine Wargames Foundry 28mm Gladiators to fill your arena.