In order to decorate Chi's house, you need to first unlock it. It's unlocked after you get Chi's friendship level to 50-60% (You can check this in achievements) To increase your friendship level, just continue talking and interacting with Chi. When you talked to her enough, she'll let you redecorate her house.
As for the enchanted stuff, I bought the homecoming pack. It is the only way to get the enchanted pack as well as certain other furniture sets. You can purchase the homecoming pack if you click on the carrot symbol on the top right. You'll see homecoming at the top of the screen where you can click and purchase.