The Spirit joins us to Christ so we share all His gifts. The Spirit binds us in the communion of the saints. The Spirit is the earnest of our future inheritance. He is the Spirit of salvation, the Spirit of the church, the Spirit of the future.
Economy reveals ontology. Therefore we can say:
The Spirit is the gift from the Father to the Son and the return gift of the Son to the Father. The Spirit is the love that binds Father and Son in eternal communion. The Spirit is the eternal perfecter of the Father, since it is through the Spirit that the Father begets the Son and so is Father; He is the eternal perfecter of the Son since it is in the Spirit that the Son loves the Father and so is Son.
The Spirit is the Spirit of salvation, of the church, of the future, because He is the Spirit of the Father and the Son.