The house decoration should be very busy. If you want to help, you are a very good friend. I think you will be very grateful if you go. As for the gift, I think you should give it to him after he finishes the new decoration and invites you to visit. Now it is enough to just help.
As for the gift for the new house, it is recommended to bring some home decorations and festive gifts, which are good for the owner of the new house. You can give a beautiful table lamp or something.
You can choose a crystal music box with photos of your friends and couples on it. Putting it at home can also increase happiness.
You can make two real dolls, or make them together, which is enough to add some vitality.
There are many other small gifts, you can go and choose. It is recommended to help first and then give gifts. I hope it helps you.