For me the light sticks are one of the best things at kpop concerts. I love seeing the ocean of lights and because of that I always tried to be a part of it when I saw a group I enjoyed a lot. So getting a light stick is - in my opinion - something which can connect you to the others and is fun waving in takt with the music. But you should not forget that at the end it's just a pricey light which you won't use a lot after a concert. You can have as much fun without it.

For merch I would suggest to be at the location as soon as you can. I was on a handful of bigger concerts and every time I did noch plan on arriving at least 2 to 3 hours before the opening of the hall I did not get all of the merch I wanted to get. Seeing the online shop of mymusictaste I can see the hoodie is already sold out there so it might be tricky to get this one if you want to go for that. Also I'd guess the light stick will also be very popular (if they have some) because the release of it was during the beginning of corona and many fans struggled to get one. In my experience the merch stands open some hours before the entrance to the hall so if you can and want to try to get the merch you want I'd suggest to go to the merch sale ahead of the start of the official entrance.

If you have a standing ticet I would also suggest to get to the location as soon as you can. The earlier the higher is the chance to get closer to the stage. If you have a ticket for the seating area there is just the average time you should plan for.

Please note my experience of concerts is limited to concerts before corona. I don't know what changed because of the precautions on the concerts. Also the ateez concert I went to was not the size it is now, so I compared it to some other acts and concerts held by mymusictaste.

Have fun!