Help/advice needed with GRE preparation

Hello everyone, Background: I’m looking to persue Ms in finance next year from US and my gpa is not that great so I want to make sure I score good in GRE to increase my chances.

My question here is did anyone from here appear for GRE? How did you prepare, did you go to coaching classes or self study? How much time you invested in it? And how much of an impact getting a good score made in your admission process?

P.S. - I have 15 years of education and some universities still require 16, so what are your opinions on this?