You should just do what you like for your first playthrough. The game has a LOT of side & hidden content, everything from completely optional areas & bosses to very well hidden areas, items, hidden story scenes, events, etc. There's also content only available if you're on one pathway or another, so it's not even possible to experience everything in a single playthrough (there's two pathways through the game that diverge from each other in some big ways). Then on top of that, there's random events that only have a percentage chance of happening on your playthrough or not.Can someone tell me with minimal spoilers when is a good time to do side quests and go after achievements etc or should I just play the game and do what I like?
I advise just not worrying about it. If you want to find hidden stuff, just explore everywhere, because there's literally side & optional stuff everywhere. Some of it obvious, some of it not. Just play how you want to play.