This is where most “almost right” situations happen. Someone wears a white business shirt with a black bow tie and thinks the job is done. The problem is that a business shirt usually has a softer collar, visible buttons, and button cuffs, which looks less formal in evening light. You can get through an event like this, but if the invitation explicitly states the black tie dress code, it is worth doing it properly, because the shirt is what builds the impression of formality around the face.
If the event is very ceremonial, a strictly evening shirt is an excellent choice, such as Koszula Gala. It is an example of a shirt that does the work at first glance: it looks different from a daytime shirt, works better with a bow tie, and has a more formal character. In practice, this means that even if you are not a bow tie person, the whole look feels coherent and natural.
Bow tie: black, ideally in silk. A self tied bow tie has one advantage that is rarely said directly: it looks alive. It has a subtle asymmetry and a slight softness, so it does not feel like a plastic rental accessory. If you are just starting out, practise tying it a few days before. Hand on heart, the first three attempts can be irritating, but after that it is just muscle memory.
And what about a necktie? In classic black tie, no. A necktie is a daytime and business accessory, and here the point is an evening convention. If you have a “black tie optional” situation and you know most guests will be in dark suits, you can consider a silk tie, but you are formally dropping down a level. If you want to stay in the evening spirit, it is better to choose a bow tie and be done with it.
It is also worth paying attention to the collar. With a bow tie, a kent or classic collar that is not too spread looks best, so the bow tie does not “sink” into it. A collar that is too wide can make even a well tied bow tie look small and get lost. One more detail: the top button should be fastened. It sounds trivial, but at galas it is one of the more common slip ups, especially when it gets warm and someone loosens the collar “just for a moment”.