The word guledic, I see it pop up frequently as either an epithet or title of Briton lords during the dark ages, yet I still haven't figured out what it means. To the best of my knowledge Ri means King, Tiern is Prince, but the definition of guledic escapes me, the best translation I've seen saying "chief" but that was a very specific example it was referring to.
'Guledic' sounds anglicised to me (e.g. Owain Glyndwr becomes Owen Glendower in English). 'Gwledig' is, I think, the word you are looking for. This is sometimes written 'Wledig' because Welsh has mutations, in which words change subtly depending on context. 'Gwledig' is related to 'gwlad' (land/territory/country) and seems to denote a ruler based on this book on Welsh medieval law.