Make sure your wife can really feel your sincerity. So the gift had better be creative and special, and it's best if it's the only one in the world and hard to copy. Don't send flowers or something, it's a bit vulgar.
You can choose a photo of you and your wife, and then find a place that specializes in making personalized clothes, print your photos on it, and make it into couple clothes. Believe me, your wife will definitely like it, because women pay attention to these details. You can also order some personalized jewelry, such as a love lock engraved with your two names, or a necklace or bracelet engraved with the initials of your wife's name, which are easy to impress her.
In short, the secret is to make your wife feel that this gift is carefully prepared for her by you, and it can't be bought casually outside. PS: I think these gifts are more romantic to give at your candlelight dinner.