The best thing, of course, is to let Plotinus speak for himself. All excerpts are taken from David McKay's very helpful online edition of the Enneads (link):
First Ennead, Fourth Tractate, Section 4:
If, then, the perfect life is within human reach, the man attaining it attains happiness: if not, happiness must be made over to the Gods, for the perfect life is for them alone.
But since we hold that happiness is for human beings too, we must consider what this perfect life is. The matter may be stated thus:
It has been shown elsewhere that man, when he commands not merely the life of sensation but also Reason and Authentic Intellection, has realised the perfect life.
But are we to picture this kind of life as something foreign imported into his nature?
No: there exists no single human being that does not either potentially or effectively possess this thing which we hold to constitute happiness.
But are we to think of man as including this form of life, the perfect, after the manner of a partial constituent of his entire nature?
We say, rather, that while in some men it is present as a mere portion of their total being– in those, namely, that have it potentially– there is, too, the man, already in possession of true felicity, who is this perfection realized, who has passed over into actual identification with it. All else is now mere clothing about the man, not to be called part of him since it lies about him unsought, not his because not appropriated to himself by any act of the will.
First Ennead, Seventh Tractate, Section 3
If it be taken into the All–Soul– what evil can reach it There? And as the Gods are possessed of Good and untouched by evil– so, certainly is the Soul that has preserved its essential character.
Second Ennead, Ninth Tractate:
This earth of ours is full of varied life–forms and of immortal beings; to the very heavens it is crowded. And the stars, those of the upper and the under spheres, moving in their ordered path, fellow–travellers with the universe, how can they be less than Gods? Surely they must be morally good: what could prevent them? All that occasions vice here below is unknown there evil of body, perturbed and perturbing.
Knowledge, too; in their unbroken peace, what hinders them from the intellectual grasp of the God–Head and the Intellectual Gods? What can be imagined to give us a wisdom higher than belongs to the Supernals? Could anyone, not fallen to utter folly, bear with such an idea?
Our adversaries do not deny that even here there is a system of law and penalty: and surely we cannot in justice blame a dominion which awards to every one his due, where virtue has its honour, and vice comes to its fitting shame, in which there are not merely representations of the Gods, but the Gods themselves, watchers from above, and– as we read– easily rebutting human reproaches, since they lead all things in order from a beginning to an end, allotting to each human being, as life follows life, a fortune shaped to all that has preceded– the destiny which, to those that do not penetrate it, becomes the matter of boorish insolence upon things divine.
A man’s one task is to strive towards making himself perfect– though not in the idea– really fatal to perfection– that to be perfect is possible to himself alone.
We must recognize that other men have attained the heights of goodness; we must admit the goodness of the celestial spirits, and above all of the Gods– those whose presence is here but their contemplation in the Supreme, and loftiest of them, the lord of this All, the most blessed Soul. Rising still higher, we hymn the divinities of the Intellectual Sphere, and, above all these, the mighty King of that dominion, whose majesty is made patent in the very multitude of the Gods.
It is not by crushing the divine unto a unity but by displaying its exuberance– as the Supreme himself has displayed it– that we show knowledge of the might of God, who, abidingly what He is, yet creates that multitude, all dependent on Him, existing by Him and from Him.
This Universe, too, exists by Him and looks to Him– the Universe as a whole and every God within it– and tells of Him to men, all alike revealing the plan and will of the Supreme.
These, in the nature of things, cannot be what He is, but that does not justify you in contempt of them, in pushing yourself forward as not inferior to them.
The more perfect the man, the more compliant he is, even towards his fellows; we must temper our importance, not thrusting insolently beyond what our nature warrants; we must allow other beings, also, their place in the presence of the Godhead; we may not set ourselves alone next after the First in a dream–flight which deprives us of our power of attaining identity with the Godhead in the measure possible to the human Soul, that is to say, to the point of likeness to which the Intellectual–Principle leads us; to exalt ourselves above the Intellectual–Principle is to fall from it.
Yet imbeciles are found to accept such teaching at the mere sound of the words “You, yourself, are to be nobler than all else, nobler than men, nobler than even Gods.” Human audacity is very great: a man once modest, restrained and simple hears, “You, yourself, are the child of God; those men whom you used to venerate, those beings whose worship they inherit from antiquity, none of these are His children; you without lifting a hand are nobler than the very heavens”; others take up the cry: the issue will be much as if in a crowd all equally ignorant of figures, one man were told that he stands a thousand cubic feet; he will naturally accept his thousand cubits even though the others present are said to measure only five cubits; he will merely tell himself that the thousand indicates a considerable figure.
[T]o despise this Sphere, and the Gods within it or anything else that is lovely, is not the way to goodness.
Every evil–doer began by despising the Gods; and one not previously corrupt, taking to this contempt, even though in other respects not wholly bad, becomes an evil–doer by the very fact.
Besides, in this slighting of the Mundane Gods and the world, the honour they profess for the Gods of the Intellectual Sphere becomes an inconsistency; Where we love, our hearts are warm also to the Kin of the beloved; we are not indifferent to the children of our friend. Now every Soul is a child of that Father; but in the heavenly bodies there are Souls, intellective, holy, much closer to the Supernal Beings than are ours; for how can this Kosmos be a thing cut off from That and how imagine the Gods in it to stand apart.
Third Ennead, Second Tractate, Section 8:
Now in every living being the upper parts– head, face– are the most beautiful, the mid and lower members inferior. In the Universe the middle and lower members are human beings; above them, the Heavens and the Gods that dwell there; these Gods with the entire circling expanse of the heavens constitute the greater part of the Kosmos: the earth is but a central point, and may be considered as simply one among the stars.
Third Ennead, Fifth Tractate:
The Eros that belongs to the supernal Soul must be of one temper with it; it must itself look aloft as being of the household of that Soul, dependent upon that Soul, its very offspring; and therefore caring for nothing but the contemplation of the Gods.
We must, therefore, lay down the grounds on which we distinguish the Gods from the Celestials– that is, when we emphasize the separate nature of the two orders and are not, as often in practice, including these Spirits under the common name of Gods.
It is our teaching and conviction that the Gods are immune to all passion while we attribute experience and emotion to the Celestials which, though eternal Beings and directly next to the Gods, are already a step towards ourselves and stand between the divine and the human.