Stephen a Shopify Guru here :)
A few things I have noticed about online selling Clothing brands on Shopify are:
-They tend to use themes that showcase the product images so a theme with a large slideshow would be a good choice such as the Venture, Brooklyn and Beyond themes.
-They all tend to have their products listed in easy to navigate collections.
-They also tend to use applications for product reviews and often have blogs in place on the store talking about the products and the work that goes into these products.
Here are two great guides to help you get underway the first is a guide about generating traffic for your store https://www.shopify.com/blog/13869029-6-practical-and-proven-ways-to-drive-traffic-to-your-new-onlin...
and this one gives a lot of great tips on how to turn that traffic into sales https://www.shopify.com/guides/make-your-first-ecommerce-sale
Hope that helps, feel free to drop us a line at firstname.lastname@example.org if you have any other questions.
For product reviews I highly recommend checking out Loox - Visual Reviews. Loox helps you collect lots of customer reviews with photos on auto-pilot, and use them to drive more traffic, conversion and retention.
For fashion stores, visual reviews are very important because they effectively reduce fit and size concerns, which are the main reason people don't convert and return items.
Feel free to check out our app page and let us know if you have any questions! Happy to help :)