A look at the neo-Platonic version of God called "the One", most famously associated with the philosopher Plotinus. This can be read in Enneads, Book 6.
I. Prerequisite: Plato's Forms
Since Plotinus was a Platonist and Platonism hinges on the Forms,let's first do a crash course in the Forms.
Consider any drawn triangle, or even a carefully constructed computer triangle:
No matter how carefully drawn it is, it will always have imperfections that make it less than a perfect triangle. For example, even the computer triangle consists of pixels, and so will consist of jagged lines and other features that are not true features of triangles:
What this indicates is that any physical triangle is only an approximation of a triangle, and not a real one. The real triangle would be the one of pure knowledge; the archetype, or Form.
The same thing applies to almost everything else that exists. For example, any particular elephant might be missing a leg, or have genetic imperfections, and thus only be an approximation of its archetype. According to Plato, these archetypes really exist as immaterial Forms, and are what constitute the real world. The physical world is but an inferior copy or approximation of the world of pure archetypes.
The problem is that if true reality consists of knowledge, then this knowledge must be grounded in a mind or some kind of intellectual source.
II. The One
Consider what the most fundamental principle in the universe must be like. It must be very simple, not composed of parts or sub-principles, because if it were, then each of its parts or sub-principles would be more fundamental than it. For example, the principle of A+ B is not as fundamental just A alone or B alone. Or consider an atom. An atom cannot be the most fundamental thing, because it consists of parts: neutrons, protons, and electrons. And its parts consist of parts. Protons consist of quarks, and so on:
So the first principle, the bottom-most layer of reality, cannot consist of parts. It also cannot be changeable, since change throughout time would be more complex than a homogenous and unchanging thing:
III. The Intellect
However, the Forms must be anchored in it somehow, since they are pure knowledge and pure knowledge cannot just "exist" on its own, but must exist in an intellect. But the One is utterly simple, so how can it contain all these complex archetypes? The answer is that the One is not intelligent. Rather, an intellect emanates or proceeds out of it, and it is in this secondary principle that the Forms are grounded:
IV. The Soul
But this is still not enough to explain the world. If we have a simple One, and an Intellect in which Forms are grounded, all we have are static forms and all that would exist are immaterial Forms of knowledge. But we see physical objects and animals changing, coming into being, passing away, and going about their daily activities. So there must be a third principle which emanates from the Intellect which instills activity in things:
So we have from Plotinus a Trinitarian God which consists of the simplest first principle, an intellect to ground the Platonic archetypes, and a source of movement and activity.