If you want to work before you become an entrepreneur, I would think you have two choices of what to do. One, become an IBanker to build as big a pile of cash as you can before going on to your own thing. Risks - burn out, that the pay leaves the industry (I think that is much higher risk than many give credit), get sucked in... Advantage - you learn how to finance things for the future.
Two - do something along the lines of what you want to be an entrepreneur in. You can always find a banker wanting to escape being a banker to partner with, so if you have skills and ideas, a job that builds the skills around what your long-term idea is will be way better. To that end, it could be anything - marketing, IT management, strategy, Corp Dev (which is basically IBanking to be honest).
So really I don't think there is a correct answer, other than to focus on something that sets you up best for your LT goal. "Entrepreneurship" includes everything, so without knowing what your ideas are, it is very difficult to point towards the best path to build up to the plan.