Whether you’re planning to design and manufacture the clothes yourself or are planning to buy them in wholesale from a designer, start small and keep things basic, growing instead with your demand.
You should also collaborate with external sources if you can.
Include in your plan an outline of who is in your business and what they do for your business.
It’s a much simpler route to take than trying to come up with a whole catalog from scratch.
You can start with a fixed figure for your funding, and then try to figure out how you will spend it.