I' am planning to get CISSP or GSEC . Please advise me on what would be the best certification to acquire first?.

While I am not very familiar with GSEC, I can safely say that CISSP is the more well-known cert for security. You do need need to have at least 5 years of experience in 2 of the 10 domains of CISSP, do earn the degree.
However, you can earn the Associate degree by just passing the exam.

IMHO,

CISSP is a better cert if you work on the theoretical and policy side of security.

GSEC is better if you are a practitioner.

However, has stated before, CISSP will likely be more successful in job hunting and getting past HR.

As someone who is regularly on the hiring side of the equation, either doing my own hiring or helping clients staff positions, I would say that the CISSP is going to get you more bang for your buck in most cases.  It isn't as drastic a difference as it used to be, but the gap is still there. HR teams have the CISSP on their cheat sheets as being "the security cert" and they probably wouldn't recognize the GSEC.  Again, this is just in regards to a random, vanilla position in "security".  For the more technical positions, or in organizations where the hiring manager has a chance to be involved in candidate screening, the GSEC might giver you a slight edge, but in most cases some HR resource that can barely boot their laptop will still be the first level of approval for your resume.