As you read more papers you should
(Consult your advisor!)
Only goal: Should have enough material for telling a good story.
Good Story: Enough (CSE) depth, enough (CSE) breadth.
Q: ``What is the most difficult CS problem in all this?''
A: The most difficult problem is X, and here is why it is hard/deep/challenging...
Q: ``Why have you looked at just one approach?''
A: Because it is supposed to be the most promising one, and it is very good/clever/deep enough in itself.