Dark suits, what are the rules of dressing and what brands do you recommend?

Dark gray suit and turtleneck knit, I want to incorporate it in warm biz style

The classic warm biz suit and knit combination. The achromatic dark gray suit can be styled with a wide variety of colors, regardless of the color of the knitwear you choose to match as an inner layer. To further enhance the sophistication of the suit, it is important to pay attention to the color of the slight weave in the gray base. For example, a gray suit with a brown weave blends well with a brown knit.

Dark suit style (3) Dark navy suit

Plain dark navy suits can be worn with a patterned tie.

Plain single-piece dark navy suits can be used in a wide range of situations, from business to attending wedding guests. If you wear a standard shirt, such as a white shirt or a saxophone blue shirt, you can easily match it with a strong patterned tie.