Deific Energy comes from the emotional thinking of intelligent creatures. Deific Energy produces energy flavored with the emotions and subjects of the thinking that creates it. For example, looking at a beautiful rose will produce Deific Energy flavored with the "Zones" of Rose and Beauty. Depending on the person, it might also produce energy flavored with Flowers in general or even a particular idea associated with roses in certain circumstances. For example, if roses are strongly associated with a prominent queen or knightly order, a person might produce Deific Energy flavored with the Zone of that particular queen, dynasty or knightly order.
How do we measure Deific Energy? Well, very imprecisely. There's obviously no objective way to measure the frequency, duration and intensity of emotion across even a single individual, much less an entire society. Remember that the rules are not important. The following calculations are presented solely so we all have a basis for comparison and can estimate the unmeasurable. Please keep these calculations in mind as you develop your Deity, but don't let the tedium keep you from participating in the first place.
Remember that Deific Energy is produced flavored in different Zones based both on the number of people who feel emotions related to that Zone and the depth and frequency of those emotional associations. With that in mind, consider a small village of people, completely isolated from anyone else. They have to struggle to survive against all the basic threats (e.g. disease, bandits, weather, starvation), but the one that is most constant among all peoples is food: some civilizations will have bigger or lesser problems with disease or weather, but all societies require food, and essentially all societies tend to grow to the point where they must struggle for food.
So, we start with a basis for comparison of one thousand average people in an average tribe or village as described above, and the frequency and duration of their emotional associations regarding the staple food crop of that society (e.g. rice, potato, etc.) over the course of a year. That amount of Deific Energy is one point. This is obviously completely subjective, but if someone has a better way of trying to measure this, feel free to propose it. The rules are not important anyway, this is just a guideline so we have a standard of comparison.
The vast majority of Zones are not produced at a rate of one per person per year, because very few Zones are as important as the staple food crop for a given society. Of course, certain individuals might produce a large amount of energy of a specific Zone - someone who obsessively tends orchids will produce a considerable amount of Orchid energy, for example. Putting a number of such individuals is one place is one way to amplify the power of a very specific Zone.
To find out how many points a particular Deity has, go through each Zone and figure out how more or less important in a given society it is in comparison to the basic food crop (or crops) in that society. If you decide it is half as important, for example, then each 1000 people in that society produce half of a single point each year. Deific points are not storable - you must use your points in Manifestations or lose them. This means that you can add up the points for a given Deity at any given time, and the total of their Manifestations and Presences should be no more than the current total of the Deific Energy. If a Deity loses followers or the intensity or frequency of his worship decreases or the number of Zones the Deity possesses decreases, the Deity may need to cancel Manifestations immediately.
Using this standard of comparison, a Demigod could have as little as one Deific point. If there is a society of exactly one thousand people who are completely normal, the Zone that is their basic foodstuff has precisely a 1% chance of producing a Demigod every Generation. This 1% chance only occurs assuming a Deity does not claim the Zone. If the society had exactly two thousand people, but everything else was the same, there would be a 2% chance. If there were one thousand people, but they were precisely twice as emotional regarding their basic foodstuff (perhaps there is only one foodstuff in this entire society), then there would still be a 2% chance. At ten points, or ten thousand average people and their average foodstuff, the amount of energy produced is officially capable of producing a True Deity. There is still only a 10% chance of this occurring every Generation, assuming an already existing Deity doesn't claim it.