Event groupings

How are event groupings done? I am in a group where 24 of the top 25 players are either challenged or champion. I entered this weekend as a diamond 1. As far as deck strength I’m at 23,900 by far one of the lowest with most over 30000 some, like the top few are near 35000. No way I’m making a dent in this group. I’m used to being top 20 and if I spend some gems I can make a run at top 5. But with this group there is no sense in me spending gems. Maybe with the rank reset I will get pushed down into a bracket where I can compete.