There is no magic bullet. On the one hand, a 4.0 GPA does not guarantee an interview much less a job.
On the other hand, a 3.4 is not a death sentence either. In general anything above 3.5 is fine. Make sure you list both your GPA and concentration GPA... if your GPA is 3.5 but your concentration GPA is 3.9, you have a story to tell.
Much more important than grades (I think) are internships and past experiences. Actions speak louder than words.
Having an inside champion (a person that can support your application) is also important.
Done...
There is a more basic question. Why do you want investment banking job? Is it salary, prestige? Or is the the job itself? The latter is much better answer than the former. If you simply like the perks of the job you are in for a rough ride. If you like the job itself, you will find many ways to approach it.
If you "love" the job, then you need explain what have you done to prepare for such a career, job.
For example.
How many investment bankers do you know?
How many of them would answer a phone call from you?
Have you interned at an investment bank?
Have you taken a directed study on the subject?
Have you volunteered at local foundation? Startup accelerators etc?
How many local organizations are you a member of?
Have you taken online courses on the subject? Podcasts, seminars?
Are you familiar with the deal flow in your local community?
Have you taken courses on Real Estate, Valuation?
If you just discover your passion, no problem.
Using a sports analogy. You are applying for a spot in the team. You are competing against candidates that have been playing / preparing for the game since high school. They have gone to the gym, cross trained, etc. How does your application compare? You are not disqualified just because you just started. There are many examples of late bloomers.
But you will have to convince the coach to give you a chance to try out. Make sure your first job(s) are stepping stones into the path.