I'm all little out of mainstream chess at the moment, but my impression was that King's Gambit is not popular anymore. In no particular order, I've found these openings popular in tournament play: French defence, Sicilian, Scandinavian, caro kann, Pirc defence, Queen's Gambit (both accepted and declined), Ruy Lopez.

Online chess streamers have also popularized dubious play and trap-setting, so those are scenarios you might want to mentally prepare for.

If it's a in-person tournament, don't ignore the psychological factors. If it's a different time control than you're used to playing, play that time control.

Best of luck!

Is there anything I can do at a consistent 1000 ELO online rapid? I've been meaning to study up to go further and have a few books. I'm sure it's not what you had in mind and I will have glaring flaws that you won't find helpful.

Haven't played chess since I was a teenager but that sounds rad, hope you wipe the floor with em. From what I do know 2000 is not bad at all. Good luck comrade!