Learn Spanish (Latin America): Tú tienes mucha suerte.

In Spanish, you "have" luck rather than "being" lucky. To express certain states like being lucky, hungry, or sleepy, Spanish uses the verb tener (to have) followed by a noun. So, tienes suerte literally means "you have luck."

Why does it use mucha instead of muy if the translation says "very"?

Because suerte is a noun (luck), you must use a form of mucho (a lot of) to describe it. Muy (very) is only used with adjectives. Literally, the Spanish sentence translates to "you have a lot of luck."

Why is it mucha instead of mucho?

Suerte is a feminine noun, so the word for "a lot of" has to change to match its gender. Words ending in -e can be tricky since they don't follow the typical -o (masculine) or -a (feminine) rules, so it helps to memorize this one as la suerte.

Do I have to include Tú at the beginning of the sentence?

No, it is optional. Because the verb form tienes is only ever used with tú, the listener already knows who you are talking about. Including tú here just adds a little extra emphasis, like saying "You are very lucky."