Depends on what you mean when you say "Professional"
You typically have two avenues in Menswear; Classic Menswear ( Suits, Sportcoats, Shoes, Shirts, etc) and Streetwear ( Tees, Sneakers, Denim, Casual Wear)
They can intertwine as people mix sportcoats with denim and boots, but when you say professional, I assume you are referring to the former?
If that is the case, I think a Navy blazer is always a good versatile piece to own. Try to stay...