I would recommend you take the gap year and study for the LSAT. Your GRE and GPA are usually not considered competitive for a T14 school (your GRE is equivalent to a 162 LSAT while you usually would prefer a 170+ LSAT, which is around 97th percentile, for T14). Unless you have some very solid extracurriculars or letters of recommendations you are probably not going to get admitted to a T14 law school. Your master in economics is good, but won't save you from your GPA and GRE. So, if you are sure you want to go to law school and go to a T14, I would recommend taking the gap year, study for the LSAT and take the exam next year. A good LSAT will not only help you with your admissions, but could also open the door for valuable scholarships.

I don't think you should wait for your green card before applying. I am also an international applicant from Canada and all the admission officers have told me they don't care if you are an international applicant or American citizen as long that you demonstrate you have adequate English skills for law school, but as you've completed your undergrad in the US, that should not be an issue for you. If you think you could get a better LSAT score by waiting for the next cycle then that could be a good reason for delaying application, but don't do it because you think that your green card will help your chances. Hope that helps!