It would not be fair to say that here Justin ranks the Holy Spirit after the angels: other passages, to be quoted later, show that this is not his meaning. It is rather that the angels are brought into prominence as the escort of the Son, to whom Justin again and again insists on applying the title "Angel" in the sense of divine messenger,  especially when he is explaining various passages in Genesis as manifestations of the divine Son to the patriarchs. Justin's immediate purpose was to show what a wealth of spiritual powers Christianity could set out in contrast to the "many gods" -- the demons -- of the heathen world: how absurd therefore it was to call Christians atheists. The same argument is handled thirty years later by Athenagoras with Justin's language in mind, but with more caution. Father, Son and Spirit he mentions in due order: but he adds: Not that our theology stops here, for it includes a multitude of angels and ministrants to whom the heavenly bodies, the heavens themselves, and our world have been entrusted by the Creator.  He has retained Justin's argument, but he has carefully avoided the imperfections of its expression.
A little later Justin returns to the charge of atheism, and, having described the kind of worship which Christians offer to the Creator of the universe, he goes on to speak of Him who has taught them this, even Jesus Christ, who was crucified under Pontius Pilate, and whom they had learned to know as the Son of the true God; "having Him in the second place, and the prophetic Spirit in the third rank."  Such language would have been challenged in later times as unduly subordinating the Son to the Father and the Holy Spirit to the Son; but it is of value as correcting the impression which might have been derived from the earlier passage in which the Holy Spirit was mentioned after the angelic host.
Towards the end of the Apology Justin touches again on this order of the three divine Powers. He finds it in Plato, and gives it as one of several proofs that Plato had read but not understood Moses. Plato had read of the Brazen Serpent which Moses set up "on a sign" (en semeio), but had not understood that the sign was the cross: he had taken it as the form of the Greek letter Ch, a chiasma (i. e. "St. Andrew's cross," or a saltire, as we say in heraldry). Moreover he had read in the first chapter of Genesis that the Spirit of God moved upon the waters. Accordingly, says Justin, "he gives the second place to the Word that is from God, whom he declared to have been extended saltire-wise (kechiasthai) in the universe; and the third to the Spirit who was said to move on the water." 
In the closing chapters of his First Apology Justin describes, in language such as his heathen readers might understand, the Christian sacraments of Baptism and Holy Communion. He gives a paraphrase only of the baptismal formula, perhaps with a view to lucidity, but possibly also through unwillingness to give the actual words.  He does not even use the terms "baptism" and "baptize," but only speaks of "making the washing" or "bath." "For in the name of the Father of all and Lord God, and of our Saviour Jesus Christ, and of the Holy Spirit, they then make the washing in the water."  He uses similar words a little lower down, with some additions: "There is named on him the name of the Father of all, etc. . . . And in the name of Jesus Christ, who was crucified under Pontius Pilate, and in the name of the Holy Spirit, who by the prophets announced beforehand all the things concerning Jesus."  This last addition is of special interest in view of the ultimate inclusion of "Who spake by the prophets" in the Creed.
In describing the Eucharist which followed after Baptism Justin speaks first of the people's prayers: "We make prayers in common, for ourselves, for the person baptized (lit. enlightened), and for all men everywhere." These "common prayers" are followed by the kiss of peace. Then he who presides over the brethren (Justin avoids any technical term such as "bishop") receives the Bread and the Cup, and "he sends up praise and glory to the Father of all through the name of the Son and the Holy Spirit, and makes thanksgiving ("eucharist") for being accounted worthy of these gifts from Him;" and this he does "at some length." "When he has completed the prayers and the thanksgiving, all the people present respond saying Amen." 
We note that the Holy Spirit is only mentioned in reference to the offering of praise to the Father "through the name of the Son and the Holy Spirit." When he goes on to describe the character of "this food, which we call Eucharist," there is no reference to the Holy Spirit, but only to the Word of God so far are we from that Invocation of the Holy Spirit for the purpose of consecration which came into the liturgies two hundred years later.
Presently Justin says: "And over all our food we bless the Maker of all things through His Son Jesus Christ and through the Holy Spirit."  Once again we observe that praise is directed to the Father through the Son and Holy Spirit.