Starting a clothing brand is not for the fainthearted.  There is much to do especially when you consider that you have no structure to  begin with and you have to create an entire business from scratch.
These days it is even more challenging.  Because getting stores and direct customers to buy a new brand is difficult.  The industry is not really growing. So in order to buy your line the buyers need to stop selling someone else.  While it is difficult to build a successful brand,  it is not impossible.  By following these steps you increase your chances of success.
The very first thing you need to do is decide what you brands product will be. I am a big believer in focus. Especially when you are new.  You are better off having less categories and more styles in the category you are in.  I have a client that started his brand with men’s, women, and children.  However there were only a few styles in each division.  When we started working together I had him focus on only women and make a more complete line.  The buyers loved it.
Then  you need to research the market and find out everything you can about how your product fits in the category.  If you are making dresses for example you want to study all the companies that would be competition for you.  Do a competitive analysis on the 5-10 leading manufactures that your customer would buy?  Then you can figure out what your USP (unique selling proposition) is.  What makes you stand out against the competition?
Study your customer completely.  What are the demographics of your consumer? What are the psychographics? “Your customers are the lifeblood of your business. Their needs and wants impact every aspect of your business, from product development to content marketing to sales to customer service.”  (John Rampton quote).  So make sure you know them as intimately as possible.
Make a business plan.  Business plans are a must.  You need to plan every aspect of your business from sales to production to marketing.  Leave nothing to chance.  Business plans also help you determine the finances of the business.  How much cash do you need to have on hand and what is your cash flow?  You can always refine your plan as you build your business.  It doesn’t have to be set in stone.  Doing one will give you a leg up.
If you want to start a new fashion brand doing these steps you will have created a blue print for your brands launch.