You can refer to the following options:
The first kind, suit, tie and leather shoes, is the most solemn and formal.
The second type, shirt+pants, monochrome (such as black, navy blue, dark blue, khaki, etc. ) slacks are also ok.
A third solid color T-shirt, such as a Polo shirt, can also be paired with solid color jeans. It is best not to wear collarless clothes, because collared clothes will be more formal.