It is never a good idea to overstay your visa.

Officially, the Schengen visa allows you a 180 day "period" beginning on the day you first enter any country within the Schengen zone with a maximum of 90 days in all Schengen countries. After you hit 90 days (in one go, or in several chunks if you leave to non-Schengen countries & come back), you can't enter any Schengen country again until your 180 period ends. And on day 180, no matter what, you have to leave Schengen territory (even if you haven't used all your 90 days), but you can then turn around & come back in again the next day & get a new 90/180 day period.

As far as risks, nothing may happen....at first. But an illegal status will bar you from doing many normal things like have a bank account, rent an apartment, register, or hook up utilities. If you are found out, you can be deported, and barred from re-entering the EU. This is pretty unpleasant and not usually worth the risk.

The guide to Amsterdam is a good place to start on figuring out how to legally stay in the country. Consult the visas for the Netherlands section, or our article on "Obtaining a Visa to Live, Study and Work in: Schengen Area".

Options include:
Study visa (have you complete your studies? )
Work Permit (what skills do you have? Have you applied for work?)
EU Blue Card

I strongly recommend you check out these visa options rather than overstaying your visa. Consult with the Dutch embassy before leaving to get advice and hear more about your options. Good luck!