How much hike should you go for?

This is a very personal question and requires a lot of skill and experience. If you are less than 3 years experience, it’s not hike that should matter to you, but a job where you will learn with a solid foundation and good exposure. In that case just mention “whatever’s best as per your standards, I’m more inclined towards a good career opportunity”. Most likely the HR will revert with highest possible pay if your interview had gone very well.
If you would have quoted ‘x’ amount higher than that, now you can imagine why you would’ve been rejected, or even worse put on hold. If you would’ve said lesser than ‘x’, definitely you would have missed a good bargain.