John Wick: Chapter 2 : Is watching first movie needed?

How much does this movie involve what happened in the previous movie, is it "necessary" to watch the first first?

You should watch the first movie.

I wouldn't say it's necessary but it definitely helps to have seen it beforehand when they make callbacks to the first. Not to mention that the first is just a really solid action flick and is worth seeing. You should be able to follow the second one fairly well though.

No but it's absolutely awesome so idk why you wouldn't want to anyways.

You don't need to but you should. You won't be disappointed.