Career/Intern Advice Needed

Backstory: I applied to a few firms and corp. finance departments where I had some small connections, nothing bulgebracket, and I got turned down at all of them, citing my G (2.5) as the reason. This is terrible, I know. Long story short, I wanted to be an author, didn't bother in HS since I was gonna write all my life, got to college, same attitude, etc.

When I finally got my act together, changed majors and started working on my grades, it was too late. At least in the short run, I have a 3.9 this semester and looking to graduate within the 3.3-3.7 range overall, and probably a 3.5-3.8 major GPA so I'm not too worried about the future. (end backstory)

I am, however, worried about my current situation; having very few options for an internship now, as in, graduating with no relevant work experience.

While my GPA isn't a good reflection of it, I'd say I'm pretty intelligent (high test scores with very limited studying) and I'm a very fast learner. I've learned valuation, modeling, etc. I know accounting (my family are accountants) and I'm interested in economics. I start my days off with headlines relevant to the industry, etc.

I've managed to scrape together a few things to make the summer not a complete waste. Mainly, commercial banking and an economic research position with a professor at my school. I'm wondering what I should prioritize in terms of opportunities?

Would the commercial banking be better experience than research assistant with a professor? How about an accounting position somewhere? Tax accounting more relevant than public, etc? These are the questions I'm faced with and stuck on. I'm a junior so I have, at best, two summers for internships left before I'm on the job hunt.

My school literally has no alumni directory, the finance clubs are accounting dominated, very few internship opportunities there. The rest of my networking connections are commercial and accounting.

My dream/goal is to end up in BB banks/M&A, head to PE, and I'd love to finish my career with a job in the fed somewhere. (I know the reality of this)

Thanks in advance and I'm open to all suggestions and criticism.