A thirty day quarantine is a good idea. Just to make sure the new budgie is not sick and not showing it yet.

That way they can get used to hearing and seeing each other. Keep them in separate cages. No one will feel bad about which cage they are in.

When you are ready to put them together, you will want to watch them to make sure one does not hurt the other. It probably will not happen. They will probably be just thrilled to get together.

good luck with cheering you