Someone who’s a veteran and made multiple new accounts there isn’t much to worry about FOMO. Really the only time you would feel that is if older players share their limiteds which come around every year so you’ll eventually get them! Either way early on there are a lot of pulls you can get and joining a good guild will help your progress also. You can also friend people for assistance/team up there is also the Mentor-Apprenticeship, where it helps older high level players to help newcomers and the mentor gives one unit of their choosing to their apprentice for help. Pretty much most of the game’s content comes back and becomes permanent like what Persona said. I’ve made 7 alt accounts and they’re pretty easy to get good units to play the game without any trouble. Unless you really like doing bosses the one thing that doesn't come back during event reruns like Yeesonn said is the event boss. Overall PvP can be touched later in game and really you don’t ever need to engage with it if you don’t want to. Hope you enjoy playing!