-While the Faith of the Seven believe there are multiple hells, the Followers of R'hllor believe there is only one 'Hell' - The current world which we live in, which was made by the Great Other, an evil god of cold and death.
-The Lord of Light wants to save the people of the world from this hell - For the Lord of Light is most the gracious, most merciful god of heat, light, warmth, and shadow.
-In his divine mercy, so that they might free themselves from this hell, the Lord of Light gave the spark of the divine to the people of the world, imbuing them with certain gifts and traits.... Learning, literacy, prophecy, mathematics, magics, the sciences, architecture, farming, all of that which separates man from beast are the spark of the divine, and his gifts to us.
-The Lord of Light gave these gifts to people in equal measure. No people are greater or lesser than any other, as all are equal before the Lord of Light. All peoples have varying and different gifts which they used to form their cultures and peoples, which are themselves reflections of how the people use the divine gifts the Lord of Light has given them.
-To the Valyrians he particularly gave the gift of leadership, that they would lead the people of the world in to a new and blessed era. Because of this, they are sometimes referred to as "The Children of Fire". As a sign of this, the Lord of Light gave to the Valyrian people the gift of dragons, Fire Made Flesh, as well as the sciences/magics of their era they used to build their great empire and make such things as Valyrian steel and the magnificent and amazing architecture they made.
-The reason for the Doom is because the Valyrians fell from the grace of the Lord of Light, casting him aside for the worship of false gods and becoming rulers of men for themselves and their greed and material desires, and thus served the Great Other and not the Lord of Light. The Doom was the Lord of Light's way of taking back the gifts of dragons and the knowledge of how to make all manner of things they did.
-The entirety of our existence is a choice. By choosing to exist, we all serve either the Lord of Light or the Great Other, regardless of whether we know it or not. (This does not mean that all nonbelievers automatically serve the Great Other)
-Those who do not have knowledge of this fact that we all serve regardless of our own beliefs(i.e. nonbelievers) are not condemned or vilified, they're simply considered unawakened - "asleep", spiritually.
-Believing in the Lord of Light is also knowing that no matter what, we all use those divine gifts given to us to either serve the Lord of Light, or the Great Other.
-Knowledge of those gifts is knowledge of the self. Knowledge of the self is knowledge of your place in the world. Knowledge of your place in the world is knowledge of the blessed plan of the the Lord of Light has for you, and by extension us all.
Some side notes on the dragon egg I'm also pondering... Fire = Life, Blood = Life... Daenerys hatched three dragons with fire, and the blood/lives of three people... Khal Drogo, her unborn son, and the witch who betrayed her. That would almost seem like life for life is necessary.
And let's also remember... Viserion(the dragon) is still out there, in this story. The other two dragons died in battle but Viserion merely "Flew away, supposedly to Asshai"...Which is another big place where the worship of R'hllor is key. Either way, there's no saying that dragon doesn't come back.