It directly translates to "you like very much", making "muy" the most accurate adjective to describe the level of liking.
Here's an example:
* Te gusta mucho el helado. (You like ice cream very much.)
You could also use other adjectives that express a similar level of liking, such as:
* Te encanta el helado. (You love ice cream.)
* Te fascina el helado. (You are fascinated by ice cream.)
However, "muy" is the most straightforward and commonly used adjective for "te gusta mucho".