in the end of the day what you are proposing to sell is nothing new, they are clothes which will have your brand on them.
Question: how are you going to make them different and/or make people want to buy and wear them?
Answer: with everything commercial it comes down to marketing!
and marketing is expensive, competitive and very time consuming.
List of things to consider are:
Product Design
Manufacturer
Product Photography
Pricing Structure
Graphic Design
Marketing
Target Market
Sales Outlet - Online/Physical
Payment Options - I assume Crypto will be one of them
Distribution