How much of the Klingon language being spoken today was actually used on the series?

Marc Okrand, who invented the language, was a consultant on all the TOS Star Trek movies. He made sure all the Klingon spoken was canonical, and if the actors flubbed their lines, he retconned them.

Okrand was not involved with the Klingon used on the TV series. As a result, the TV series featured words like wIjjup for “my friend”, where –wIj is supposed to be a possessive suffix. And that’s when the script writers bothered to use the Klingon Dictionary at all.

Be hesitant with TNG for any Klingon utterances you hear that are one word long. Don’t take seriously anything more than one word long.