Need some advice on finding patterns/fabric Sewing Machines Parts and Sales in Los Angeles

I am looking to get into some serious sewing. I want to be able to make my own clothes but I don’t know where to look for the right fabric and patterns. I’m fairly inexperienced but I’m usually pretty good at self-teaching (ie watching/reading tutorials). What I eventually want to be able to do is sew things like this:

http://bananarepublic.gap.com/browse/product.do?pid=183617002&vid=2&locale=en_US&kwid=1&sem=false&sdkw=ryan-fit-dot-slim-straight-pant-P183617&brandCvoSid=DMVXZBTHBV4B&sdReferer=http%3A%2F%2Fwww.bananarepublic.com%2Fproducts%2Ftall-womens-pants.jsp

My question is: Where would one go to find the appropriate fabrics for such a project? I know most fabrics like the one used in the link are specifically designed and made for large retailers but I just need a similar type of fabric in terms of texture/stretch so that it’s appropriate for the article of clothing I’m trying to sew.

Also, I know that this type of thing is probably too complicated for an amateur to sew but mostly I just want to know where to get good fabrics and possibly patterns.

Any guidance would be greatly appreciated.