Don’t worry about Patreon.
There is no paywalled content, just the priviledge of playing the new content 3 days earlier.
Updates are every week, Mondays for supporters and it goes public the following Thursday.
As for the costumes, it depends which ones you’re missing.
In the case of Pixie, you buy most of her outfits. And the one that is predominantly green, you get by triggering the halloween easter egg.
(You do that by buying the halloween themed furniture and setting it in your room)
Just sleep for a few days to get Pixie’s. Gwen and Jessica also have a halloween costume, but their event happens if you go to the dungeon at night (while having the halloween decorations in your room)
Let me know if you’re missing more of them, I can’t be arsed to write the complete list of unlockable costumes.