Shirts generally have the design of button-down the front either half-way or all the way, and a variety of collars. The standard pointed collar shirt is perfectly acceptable and in wide use. Alternative collars help to encourage a more historical and unique look, and they work better with different kinds of ties. Colors of steampunk shirts are not limited. A variety of colors are included. However formal and high-class occasions demanded white. Beige is popular in explorer and working-class outfits to convey a sense of practicality and hands-on experience.
Dark colored pants are standard for any formal or high-class look. Lower-class costumes might use khakis or cargo pants. Jeans are a basic no-no for steampunk, unless perhaps you are creating something from the Weird West, although even there they are only appropriate for the extremely low-class.
The shirts and pants are most basic to men’s steampunk apparels. You can take what I mentioned above into consideration when you want to dress in steampunk style.