COMMODUS: The first thing I shall do…is honor him with games worthy of his majesty.
This is the first of many ironies in Commodus' behavior. He wants to stage a huge spectacle to honor his father, and yet it's clear that this is something his father would not have wanted.
COMMODUS: A vision. I will give the people a vision and they will love me for it. They will soon forget the tedious sermonizing of a few dry old men. I will give them the greatest vision of their lives.
Commodus plan to manipulate the people—to win their hearts—is to "awe" them with the visions of gladiator combat in the arena. It's a smart plan, but it will backfire.
SENATOR GRACCHUS: Rome is the mob. Conjure magic for them and they'll be distracted. Take away their freedom, and still they'll roar. The beating heart of Rome is not the marble of the Senate, it's the sand of the Colosseum. He'll bring them death, and they will love him for it.
Gracchus hits the nail on the head with this one. The "death" and "magic" Commodus will use to amaze the people will distract them from how bad things are and make them temporarily love Commodus. Gracchus knows how easily manipulated the "mob" can be.
PROXIMO: I was the best because the crowd loved me. Win the crowd, and you'll win your freedom.
Proximo suggests that aweing and amazing a crowd can also lead to freedom. Commodus wants to awe and amaze to control the mob and take away freedom. Maximus will use it for the opposite purpose, and win.
PROXIMO: I know, Maximus, that you are a man of your word, General. I know that you would die for honour. You would die for Rome. You would die for the memory of your ancestors. But I, I am an entertainer.
Proximo is an entertainer, in the business of amazing the crowds. In these lines, he suggests that being a purveyor of awe and amazement is incompatible with ideas of honor. Maximus is now a business, and Proximo's job is to profit from him, not partake in some quest to kill Commodus and restore republican government.