Answer:
Dear Cousin, ( Put a name if needed)
Thank you so much for the gift you gave me. I want you to know that I am very grateful for it. You must have spent so much time working on my gift. I had no words for when I opened it and it is going to really help me in the future and if it does and goes really well I will thank you for it someway. You had no idea how much I loved your gift. You really surprised me you know? I want you to know that I love you and hope you and have a great day.
Sincerely, Your Cousin ( Put a name if needed)