What is important for a student to get certificate or to get proper knowledge?

A certificate will get you the interview, but without "proper knowledge" you are unlikely to get past the interview process. The conundrum here is getting to the interview without a certificate and being able to demonstrate your knowledge!!

Of course it is more important to get a proper knowledge than the certificate. But the certificate is also necessary and @ No.2

This is my first post here. I am an active researcher in this area. Of course it is very important that the candidate acquire the knowledge. Candidate cannot be or should not be certified if he/she has not acquired knowledge for that given certification. 

Researchers have time and time again argued that Education or Qualification (Certification) can only secure you interviews; selection will entirely depend on the soft skills and hard skills that you possess.

Some of the skills vary according to the Job and Industry, employees are expected to possess good soft skills with the expectation of very few jobs like engineering, where the technical, sector and occupational specific skills are placed higher value.

So knowledge you acquire and if you are able to successfully implement or exhibit the knowledge you acquired is more important than the certification itself.