Answer:
Before reading the examples, bear in mind that dramatic irony is a device that consists of the audience being aware of something that some of the characters are not aware of.
1. "We should have else desired your good advice (...) in this day's council: but we'll take tomorrow" Lines 20-33
Translation: " We wish you could have stayed so that you can give us your good advice, but we'll talk about it tomorrow"
We know by this part of the play, that Macbeth feels threatened by Banquo, specially because he was present during the witches' prophecy, so Banquo has suspicions about the way in which he proceded to become King. Banquo is unaware of the extent to which Macbeth's ambition has reached, he is not aware of how threatened Macbeth feels by his presence.
Moreover, we are almost certain that there is no tomorrow for Banquo.
2. "Fail not our feast"
Translation = don't fail to be present at our banquet.
Macbeth doesn't want Banquo to be present anywhere, he wants him dead. Banquo is not aware of that.
3. "We hear our bloody cousins are bestowed in England and in Ireland, not confessing their cruel parricide..." Lines 31-32
Translation: We have heard that Malcom and Donalbain are in England and Ireland and they haven't confessed that they have murdered their father, king Duncan.
We know that Macbeth killed Duncan, and not Malcom and Donalbain.
