Start with the most basic commodity knowledge:
Raw materials: plant fiber (cotton and hemp), animal fiber (wool and rabbit hair), synthetic fiber (polyester, nylon and nitrile) and blended fiber.
Grey cloth: woven and knitted.
Printing and dyeing: I suggest learning slowly in the future.
Clothing production (the key point is the process ahead): the calculation of materials, the measurement of dimensions, the functions of various sewing machines and the inspection of various defects should be done slowly.
Accessories: Use a lot of accessories, understand the functions of various accessories, and carefully accumulate relevant information.
Customer data must first be understandable and converted into production data.
The most important thing is: learn from your predecessors with an open mind, don't be ashamed to ask questions, be sure to ask more questions, don't be afraid of making mistakes, and seize every opportunity to go to the factory to learn and watch. It is difficult to make progress just by talking about theory.