Can you share the blog?
The type of clothing you are going to make is going to dictate a lot of the steps.
Something like this, however:
Step 2 is the big one. I have helped many clients with their production agreements. It is very, very rare for a company to produce its own clothing these days. You are going to want to find the company that will be able to make clothing in your category, according to your design specifications, at your price point. That's big overlap. If money is no object - I can get you set up really damn fast. However, assuming your target audience is a budget, you have to get orders made that will allow you to sell them at that price point with your own profit margin built in.
This means you are likely going to need funding. Self funding is great if you can afford it. Venture funding for a clothing brand may be harder. As may be seeking traditional loans. If you have a good relationship with your bank this may be the place to start. Additionally, I would investigate VCs, Angels or accelerators that invest in clothing startups. However, you are going to need a pretty clearly defined angle / demographic / marketing plan in order to be suitable for investment.
The reason I say all this is because the margins increase with the size of your order. And the size of your order can quickly become staggering - tens of thousands of units.
However, for the most part, it is all about establishing relationships with your manufacturers and getting to a point where you can place an order and get a turnaround reliably.
This is, assuming, you are going to be doing direct-to-consumer retailing. If you are going to be selling through other stores, that is a whole other discussion as well.
So do you have a clearly defined target demo? How many units are you planning to move? Hundreds? Thousands? What is going to be the "centerpiece" of your line? I hate to break it to you - t-shirts are as crowded as they come. Your "MVP" (minimum viable product) could potentially be something that is more of a differentiator than a t-shirt. However, those are just my thoughts in passing.