Chances are that one of the first words you learned in Spanish is gracias, the most common way to say "thanks" or "thank you." It is, of course, an extremely useful word.
If you wish to indicate what you're giving thanks for, use the preposition por to mean "for": Gracias por el regalo, thank you for the gift.
If you want to say "thank you very much," you can use muchas gracias or even muchísimas gracias. Also common is mil gracias, literally "a thousand thanks."
If you want to add variety to your language, here are examples of a few other ways you offer thanks:
- Te doy gracias por el regalo. I thank you for the gift.
- Me has ayudado mucho. You have helped me very much.
- Me ha ayudado el regalo. The gift has helped me very much.
- Me ayudará mucho el regalo. The gift will help me very much.
- Te agradezco el regalo. I appreciate your gift.
- Me siento agradecido (agradecida if you're female) por el regalo. I feel grateful for the gift.
- Estoy agradecido (agradecida if you're female) por el regalo. I am grateful for the gift.
- Me encanta el regalo. I'm delighted by the gift.