Prepping for MFE, Non CS background?

[BlackMamba]

What is generally regarded as the best place to advance your CS/programming proficiency across the various languages relevant to prospective MFE applicants? Those of you who applied to and attended a top MFE program coming from non CS backgrounds, where did you guys turn to for developing this proficiency? Coursera?

Also, for someone with a very primitive programming background, what language would be best to start with? I was looking at Python.

Thanks in advance for any insight!