I DON'T KNOW WHAT TO DO WITH MY LIFE? NEED ADVICE. PLEASE HELP.

So I have so many passions. I’m very entrepreneurial and have started a successful social media company which has 2 million users and 1.2 million seed funding. I’m 16 and in Australian and in two years I want to study in the USA. This has been my dream for so long. I really want to go to Stanford but I’m not sure what to study. I want to be an entrepreneur, but I love fashion and wall street (banker, hedge funds, day trader - big bucks and I get so inspired when I watch wall street, I love everything about it!) but then again a stable job is cosmetic dermatology and I’m really really interested in that.

Please help me decide what I should do. Can I have options? Can I study my undergrad and grad in the US if I want to become a cosmetic dermatologist? And what does a dermatologist usually study for the bachelors degree? Is it possible to still major in Economics BA and then specialise? That way I have options?

And are there any prequisities for Stanford to become a dermatologist - or doesn’t it matter what I want to be until I get a masters, phd ect?

First off, calm down. You've accomplished a lot as a 16 year old and have your whole life ahead of you.
 To become a dermatologist requires becoming a medical doctor. The ONLY way to become a medical doctor is to go to medical school, which is 4 years, after undergrad then go through a residency, which I belive is 4 for derm. Becoming a medical doctor is not a masters degree. It's long, hard, and grueling. You will probably have no life for all of medical school and the first half of your residency. It's extremely rewarding for someone who has a passion for it, but if you don't absolutely love it, you will be miserable. That's not to scare you off, but just to make you realize that becoming a doctor's not a little thing you do on the side. 
As far as undergrad work to become a doctor, you can do anything you please as long as you complete some basic science (often referred to as "pre med classes") with it. So yes you can get a BA in economics. There are even some medical schools that provide combined graduate degrees, commonly MBA, with your MD. 
I do thing that you could definitely integrate your two passions. Medicine, especially pharmaceuticals, has a lot of buisness in it. I wonder if you'd be intrested in being a pharmaceutical rep. They work to help the buisness side of medicine companies, but still have to have a good knowledge of how the medicine they are selling works. From my (limited) understanding, this is especially big buisness in dermatology. 

Thank you so much