If you don’t own a tux, you could opt to wear a dark business suit or a sports coat and tie with matching slacks.
You can also wear a black dress shirt under a sports coat.
A collared shirt, trousers and a jacket or sports coat satisfies this look.
When the warmer months roll around, a men's cotton sports coat can be the perfect addition to complement any outfit.
Unless you have a very distinctive sense of humor, your best bet is to wear a khaki colored sports coat with a similarly styled pair of pants.