"It's all gravy" therefore means that there is an abundance of good things in the given circumstance.
It should not be taken to mean that there is no problem or that a situation is liked, specifically. Those things may follow but are not necessarily connected.
B: It's all gravy from here on, boys.
Omar: In Math!? Dude, I got an "A" in that class. First I thought it would be hard, but now it's all gravy.