HOW IMPORTANT IS THE WAY I DRESS?

the most important thing about how you dress is being comfortable. If someone is comfortable then they are confident. People usually don't hand around people by the way they dress because of their own insecuritys. Believe me you want to befriend anyone who is confident enough to dress the way that makes them comfortable for who they are. A lot more to be learned from these people.

Actually the way someone dresses does reflect not just on themselves, but on people they are associated with.
If you work for a company and dress like a slob, then it reflects poorly on the company.

However, wearing designer labels is all about status. Its trying to show people that you are a so wealthy you can throw away money on clothes because of a name.
In the real world it doesn't matter, any more then driving a BMW or living in the "Right" neighborhood.
You don’t need a polo horse on your shirt or a SWOOSHES on your shoes to fit in.