Hey, maybe my backgroung will cheer you up.
I am from Czech Republic and I've been studying two bachelor degrees - one in math and other in economics and finance at Charles University in Prague. That is the best school in CR, maybe even in the middle european region, but ranks somwhere like 350 in the world rankings, so definitely not target. (However I think that such general rankings are complete bulls*** and what really matters is what you learn in the school)
My GPA definitely wasn't top, approximately 3.2 at both schools (although we have a different grading in CR and studying two degrees = 8-12 subjects per semester). Apart from school, I've had two internships, both in data analytics (IBM, KPMG) so not really MFE stuff. As for the tests, I've had 167 from GRE quantitative section, so again not top. It didn't really bother me, because the math in GRE quant compared to the math in MFE degrees is like comparing addition and subtraction of natural numbers to measure theory.
I took the GRE math subject test and scored little over 70% (with like 2 days of preparation) and since none of the programs I've applied to wanted the math subject test, I didn't retake it. However I think that the GRE subject test score examines your preparedness for MFE degree math much more than the quant part in the regular GRE. (Like really - can anyone explain to me how should your knowledge of high school geometry, arithmetics, reading tables etc. (stuff in GRE quant) determine your preparedness to take subjects such as stochastic processes, PDEs, optimization, etc?)
And this year I've got into Columbia's MFE and CMU MCU (attending Columbia).
So to sum it up - I think you definitely have a shot at the top programs if you keep doing what you wrote you plan to do. And I think that if you can score 70%+ in the GRE math subject test, it will definitely help you.
Wish you a good luck,
Marek