Although this sort of question gets asked quite frequently, the concept of hubris strikes me as a dangerous one to apply to English literature, namely since Shakespeare knew very little Greek and I'm certain he was unable to grasp the subtle nature of Aristotle's Poetics, which gave rise to this notion that if we can just find instances of hubris, then we can understand everything that goes on in tragedy.
That being said, hubris, from the Greek perspective, was a violent sort of arrogance. It's not just the sort of arrogance exhibited by some Hollywood star who acts like he or she is better than everyone else. Hubris is the sort of arrogance people exhibit when they actually do run over everyone in their way.
If, however, you are going to argue that Caesar's downfall is caused by hubris, I would say that you are on the right track to look for examples of Caesar disregarding signs from the gods. In Greek literature, when a person puts themselves on a level equal with or above the gods or having no need of the gods, they are committing an act of hubris. Thus, when Caesar ignores signs from the gods, the ancient Greeks would say he is committing an act of hubris.
On the other hand, the most talked about act of hubris in the play is one which Caesar never embracies, namely the acceptance of the crown. To accept the crown, from a Roman perspective, would have been an act of extreme arrogance.
So, actually I would argue that Caesar's downfall in Shakespeare's play is due not so much because of his arrogance, but because his enemies believed he was arrogant (more specifically ambitious). This is the notion that Antony attacks in his funeral oration and Antony makes quite a convincing case that Caesar was not ambitious (and therefore he is not arrogant).