If the invitation is to an associate’s house for dinner, good manners require that you bring a small present, such as flowers, candies, or baked goods, but no alcoholic drinks. If you bring chocolates from abroad, which are always appreciated, make sure they do not contain alcohol. Small souvenirs from your home country are also welcomed.
Despite the religious and legal prohibition of alcohol, non-Muslim Iranians (e.g. Armenian Christians) are allowed to brew and consume alcohol in private. Some Iranian Muslims also drink in the privacy of their own homes, so if you are offered an alcoholic drink, you can accept it, since your host also drinks.
If the invitation is to a restaurant, convention requires that the host pays. You may try offering to pay (only ta’ârof), but do not expect the offer to be accepted. Meal etiquette and related issues are also another aspect of this interaction.