Hi @Marhardi, nice to see you here in the community.
A Profile (email subscriber) can belong into as many different Lists as you want. But, a Profile can only belong into any one List exactly once (no duplicates).
So in other words, if you want to create a new List just for the contest entries, you can certainly do that so that new and returning subscribers can enter your contest and be added into that List.
However, just note, that also means new subscribers will only belong in this contest List, so you may want to move them over at the end of Contest, or create a Segment that represents profiles subscribed to your main List and now this “Contest List.” Here’s a great Klaviyo Article that describes some best practices for running Contests (or Giveaways) with Klaviyo:
Hopefully that made sense.