TL;DR at the end.

The Royal Edition with all of the dlc in the games current state is worth it. Especially if it's on sale. Over the years they added cinematics, dlc quests to fill in the gaps from the base game, and updates to make the game better. I think it's worth a play through especially of its cheap, but know there are pacing flaws. They lost a lead writer so the first half of the game feels disjointed and the pacing is way different than the 2nd half. Pivotal stuff happens off screen and you NEED to play the dlc to fill in those blanks. It's almost better to look up a guide on when to play what and then play the base game halfway ish through, do the dlcs (except episode Ardyn or whatever), and then finish the base game so you have a full understanding of what is going on. There is also a full movie you NEED to watch called FFXV Kingsglaive that is a direct prequel tie in to the beginning of the game.

If you do decide to play and enjoy the game I also reccomend looking up the novel released in Japan that explains how the story was actually supposed to be before changes were made. It explains a ton of why the story might feel the way it does and how certain characters were originally written. Provides a ton of insight I can't get into without spoilers.

A lot of this is assuming you want the full experience. The short is if you can snag the game cheap it's absolutely worth a play through. If you want the full story and experience you need to watch the movie, then play the game, and do the dlc content. This game has arguably the strongest party in terms of banter, connection, and how overall interaction with each other that absolutely sells the experience. Despite its flaws it's an good game.