GRE General or GRE Math

I'm currently in my third year doing BSc Financial Analysis.

I got very bad grade (D) for calculus and linear algebra during first year. Because it is a UK system, the first year results don't count in the GPA and my current GPA is 3.7/4.0. I know the grades do matter when I apply for top schools MFE.

So I would like to ask whether taking a GRE Math subject test (and good score) will help compensating the bad grades from year one? Or should I consider and work hard only on the general test?
Learn Calculus from a well-written book; gain confidence by solving more problems from Piskunov or Maron.
Applied Linear Algebra by Olver, proofs from Axler.
I think, you'd be in a better place - regardless of whether you choose to take a test to demonstrate your competency/skills.