Here's a helpful thank you card template to use as a framework for your own message:
Begin with a few sentences that show your appreciation for the guest being able to attend your wedding. If they traveled a long way or had to endure a hardship, be sure to call that out in your note.
Dedicate a sentence or two to the exact gift that was given. Be sure to name the gift and explain how you intend to use the gift. If possible, highlight how the present is a perfect choice.
Finish with some memorable words from the heart.