If you want to go into banking, apply for physics, maths or engineering and get into a top Uni for those subjects. That way you will make it easier to get into a top Uni (and a top IB as a result) and not waste a spot for someone else who wants to study economics at Uni.
"I've been interested in business/finance/econ since I was about 8" - lol, I bet you couldn't spell any of those words when you were eight. Is that what you talked about with your mates in the playground? Seriously...
100s of personal statements examples here