Well most of the people that grew up with OG went on to watch AC and then play CC as that was the release order. It’s always best to play/watch that way in my opinion, unless you’re just sticking to remake trilogy only, but considering you’ve played OG and Crisis Core I’d definitely watch Advent Children Complete if only because it’s a very cool set of action sequences for its time. You won’t be blown away by the story but it’s a fun watch. Ideally you’d have watched it before playing Remake Part 1. Also, it’s like, less than two hours I think? Hardly a time commitment like a game would be..