The story of Gladiator is about Maximus who is a general, who then moves onto to become enslaved, a slave who became a gladiator and then the gladiator who defied an empire. In simple terms the plot is simply one of Maximus seeking revenge. Also there is a sub plot surrounded the corruption and leading astray the Roman empire all for Commodus seeking power. The screenplay seems to portray a goal oriented plot structure and it 'seeks not to tell the story but to show the logic by which the story is told' (nelmes), the goals keep shifting throughout between Maximus and Commodus who maintain they are rivals throughout.
The story is written in a chronological fashion starting out with the opening scene of Maximus with his son and wife, think this was written to tell is that this is the start and the scene fades into real life where it begins to explain how the protagonist got there. The script sets up the theme and tone which seems to me to be about slavery striving for freedom along with the idea of the world being democratic and mortality. Within the first act a lot of exposition is shown. For example The German army is defeated showing Maximus as a leading general. Aurelius is then killed after he explores his wished to make Maximus the next ruler.
At first glance after reading this screenplay it follows the classic three act structure, a beginning, middle and an end. Act One sets up the Maximus as the hero and shows the first signs of conflict with Commondus who is the villain behind slaughtering Maximus family and is rival over the throne. Act two comes in