The starting point for insights into these fantastical worlds should come from the mind of a child. Jesus Christ had some interesting ideas about this.
This led me into literature/movies which were oriented towards childlike visions. Disney movies were a good start.
As teenagers, we probably assumed there were gods of light and gods of darkness behind all the crazy stuff on Earth. "The Twilight Zone"taught us lessons about Heaven, Hell and other alternate realities. "Slaughter House Five" might suggest that the universe was accidentally destroyed by a super being from Tralfamadore, but this situation would be straightened out by Dr. Who and the"Time Lords".
I found that in the original Star Trek there were lots of answers about these superbeings and the brotherhoods they belonged to. In "Errand of Mercy", the beings looked like they came from a medievel civilization, but were, in fact, so advanced they didn't need techology from the Klingons or the Federation. In "Who Mourns for Adonis", the Greek gods deserted Earth because no one believed in them anymore. In"Spectre of the Gun", the aliens used illusions of death threats to try to scare off the Enterprise. In"The Squire of Gothos", the alien used the Enterprise crew for his own amusement. In the end, his power was ended when "his mother and father" showed up and chastized him like a spoiled child.
Supposedly many Star Trek stories came from Gene Roddenberry's connection with America's Secret Space Program. The above episodes were a great introduction to advanced beings and civilizations.
Then there were far out stories about the Q Continuum in STNG and Star Trek Voyager. Suddenly, the unreal real estate of the gods took the shape of a clubhouse on the corner of "beyond" and "nowhere".
I had a certain familiarity with this clubhouse. I could imagine it being a meeting place for a gang of intergalactic bikers.
There were some good stories about Q and his brotherhood. My favourite one was "Death Wish". Sometimes being a powerful and immortal being isn't all it's cracked up to be.
Getting closer to the real world, we have "The Blue Avians" who met Corey Goode a few years ago. Their main business at this time seems to be transporting souls from one world to the next. They also have their own religious philosophy that they call "The Law of One". It isn't the easiest book to understand. The Bible by comparism is a much easier read.
Last, but not least was the Galaxy Federation's attempt to download vast amounts of information through L. Ron Hubbard. This probably happened when he went through a near death experience during WW2. This led to his quest to achieve "Operating Thetan" which some might call a free spirit or an ascended being.