Hello

You can get your gap year certificate from nearest office of law (or court) be it a district or sub district court. You can buy 100 Rs stamp certificates (at notary, sub-registrar offices, courts. ) You will have to contact either an advocate visit  notary desks near courts.

Gap certificate is needed as a proof to show why the student had taken a gap and if the student was enrolled in any other college/university at that time. It is not necessary to produce a gap  certificate unless your college asks you to.