The only way to know for sure is to get personalised financial advice from a legit financial advisor.
But there are some rules of thumb! Opting in to a KiwiSaver fund will help you save for a first home and/or retirement. So for a lot of people, it's a great option.
It does also mean giving up a small portion of each paycheck, so it's important to make sure you're comfortable with saving that money rather than spending it.