Affiliate Marketing Secrets

any idea, how do you set something like this up business wise, what i want to do is, set up a platform for xbox 360 and ps3, where people come online and play games at a price, i could probably do this from home, because i have a pc, 360 and ps3 at home, not sure what niche market to have, it is mostly teenagers or youngsters that play video games, i want to keep the idea open to all ages, how much money do you need to achieve this though, i can’t give exact figures but currently i have between 4 and 6 thousand in savings, would that be enough to start a business venture.

I’m the kind of person that knows a good bit about a lot of different topics. Sports, computers, video games, science, health, biology, chemistry, sports medicine, anatomy, guitar, etc
I know a decent amount about these things but I’m not an “expert” in any field. So how do I go about choosing a blog “niche”?