Thank Yous For Coaches How Should I Write Graduation Thank Yous?

How should I write graduation thank yous? - thank yous for coaches

I graduated from high school this year and can not write, I thank you. Some of the cards that you created for the family, I do not often see others regularly came to the family to see more, and some were my friends and relatives. I owe the idea of writing, but I'm not sure whether to write polite "Thank you for the card." My other problem is that few polite phrases that would sound too formal for me.
Another thing is that I do not know how to manage money. I was told, "I thank you for the money" should be "Thank you for your generosity, but it fits into the category of" sounds too formal.