Does Subeta has a Subeta Christmas wishlist forum? and how does one set it up? Where would it be in?

If you mean that you will be asking for other people's christmas wishes so you can give them items, that would go into Advertising > Giveaways. I see there's already someone doing a christmas giveaway there.

If you mean you want to put your own wishlist somewhere for people to give you items, I'm not sure Subeta would consider it begging or not, so that would probably not be allowed.