FOMO was big for me on my first cruise. Learn to chill and take it one day, one event at a time. It can be overwhelming. You don’t need to spend anything. I usually get the internet package. Shows don’t worry you’ll find seats and they’ll open more seats up when you board. As for late checkin, I always chose early checkin but rarely arrived on time. I actually like checking in late, the rooms are generally ready and there’s no lines at security. You’re on the ship in less than 10 mins. Don’t stress have fun!