First you need to get traffic to your site. Then you can start selling your clothes. You can sell clothes two ways, make your own and sell them, or make the designs and have a site like Cafe Press.com make your clothes and ship them out and do all the dirty work.
I suggest you make your site using a program that will get you internet traffic. I use SBI which is a site that helps you get the traffic free. You have to pay the internet company for your URL name and for hosting, but they provide the programming to make your site. I don't know much about computer website design, but was able to make a site using their programming.
My site is on running, because that's what I like to do and I also like to write. The link below explains what the website I use to design my site is all about.
Hope this long winded answer helps. Take care.
I did a quick quote for you using a company's website that I have used before. Kelgraphics, it's called. These guys have been around since 1977 and print their own shirts and other apparel in house. Very good quality, check them out!