Advice for Engineering Undergrad

Hey everyone,
Quick background, I took a bachelor's in mechanical engineering from UWaterloo and my GPA was rather poor (~3.0, didn't attend lectures, normal bs excuses etc.), I've been out of school for a couple years working in the energy industry (business dev/planning/corporate modeling) and I really want to transition to trading. However, I need advice on what to focus my time on as it seems like there's many options and deciding which is correct is beyond my available network. Would it be best to:
- go back and take a different undergrad in stats/math/CS to boost my GPA and leverage that to get into a reputable masters program?
- apply to MFE programs (seems extremely unlikely I'd get in to any of the more reputable schools, how worth it are the less reputable programs? or Programs at Canadian schools?)
-try to get whatever trading experience I can (maybe some sort of commodities desk, nat gas scheduling, or something in this vein)?

Essentially, what would be your suggested path for an unrelated undergrad with extremely mediocre grades to break into trading/quant trading?