The most authoritative source is the Master Dialogue Document (Season 3-8) created by the show's linguist, David J. Peterson. It includes the original invented language, phonetic pronunciation, and the English translation.
Season 3 can be tricky, as they are often treated as "forced subtitles" that only appear when High Valyrian or Dothraki is spoken. game of thrones season 3 subtitles for non english parts
Notice:
What you need for Season 3 are (sometimes labeled as English [Forced] or Subtitles for non-English parts ). These: The most authoritative source is the Master Dialogue