Cassius certainly places personal gain above the general good. During their argument in Brutus' tent in Act 4, Scene 2, Brutus accuses Cassius of being greedy for gold. In one place Brutus says
Let me tell you, Cassius, you yourself
Are much condemned to have an itching palm,
To sell and mart your offices for gold
But most significantly, at the end of Act 1, Scene 3, when Cassius is alone after discussing the possible assassination of Caesar with Brutus, Cassius soliloquizes
Caesar doth bear me hard, but he loves Brutus.
If I were Brutus now, and he were Cassius,
He should not humor me.
In other words, Cassius would take advantage of the hypothetical friendship with Caesar and not even consider plotting against him. Here he shows clearly that he is mainly concerned about himself. Shakespeare portrays Cassius as entirely cunning, self-seeking, miserly, and dishonorable.
Antony seems genuinely grief-stricken over Caesar's assassination. But he is a realist and a materialist who doesn't forget about his personal interests. An indication of his cold self-interest can be seen in Act 4, Scene 1, where he says,
But Lepidus, go you to Caesar's house;
Fetch the will hither, and we shall determine
How to cut off some charge in legacies.
After using Caesar's will to turn the Roman mob against Brutus, Cassius, and the other assassins, Antony now wants to see if he can cheat those same citizens out of some part of what Caesar bequeathed to them. At the same time, he tells Octavius that they ought to cut Lepidus out of the triumvirate they have just established.
Is it fit,
The threefold world divided, he should stand
One of the three to share it?
When Octavius seems to object to such treachery, Antony says:
And though we lay these honors on this man
To ease ourselves of divers sland'rous loads,
He shall but bear them as the ass bears gold,
To groan and sweat under the business,
Either led or driven as we point the way...
Evidently Antony has already been involved in actions which have aroused public criticism, and he has tolerated Lepidus as a partner because the Roman general has a sterling reputation.
So both Cassius and Antony place personal gain above the general good in Shakespeare's play.