I have never come across anything that discusses what beliefs in general people held at the time of the birth of Jesus.
Uh... okay... you do know that Roman, Jewish and other religions at that time were pretty well documented, right?
Ignorance was abundant in those times
Ignorance is abundant today. What's your point?
but was any book ever written to bring to light what people believed to be true? How old did they think the Earth was?
AFAIK most religions didn't really specify a date. I don't think they really cared too deeply. They just knew it was a "long time ago."
Because deities created them.
A typical peasant might think the Earth was flat, but lots of people at that time knew that wasn't true. The ancient Greeks worked it out, and sailors realized that land and ships receded past the horizon. The claim that "people believed the Earth was flat!" is mostly an anti-Catholic slur, started in the 17th century. (
Myth of the Flat Earth - Wikipedia, the free encyclopedia)
What was the moon and sun and stars?
Most religions believed that the moon and stars were deities. E.g. Apollo was the Sun god, and he drove the sun across the sky. Poseidon set Cassiopeia upside-down in the stars, to punish her. Ra was the Egyptian sun god. Romans thought the moon was a deity (Luna), Greeks called her Selene.
What happened after death?
Greeks / Romans believed that souls of the dead went to Tartarus, the underworld, ruled by Hades (called Pluto or Orcus by the Romans) and his abducted wife Persephone (Prosperina). There was no judgment of the dead.
Jews didn't believe in an afterlife.
Was one race superior to another?
Not in the modern racist sense, no. However, the Greeks and Romans looked down on other societies, and often called them "barbarians" as their language, to them, sounded like someone saying "bar-bar-bar." That said, Herodotus traveled to Egypt and claims to have learned much about northern Africans and others, and described them as fairly sophisticated.
The Jews believed they were chosen to represent HaShem on Earth. Not necessarily superior, but with a responsibility to do His will.
Who were the great teachers back then and what did they base their teachings on? I am not talking about the Romans and Greeks etc
Hesiod, Homer, Plato, Socrates, Aristotle, Pythagoras, Parmenides, Virgil, Heraclitus, Epicurus, Lucretius, Zeno of Citium, Epicetus.... The list goes on. Sophists were popular at the time of Socrates, Plato and Aristotle. Those WERE the great teachers.
Jews mostly followed the rabbis affiliated with the Second Temple in Jerusalem. There were also numerous wandering itinerant Jewish preachers in Judea, many of whom were suppressed by the Roman occupation.
Of course, most people didn't have much (if any) education. Teachers typically worked for the affluent city-dwellers.
I am aware of the so called great philosophers but what about the average folks in the country sides?
"So called great?" You do realize that Christianity and the West owe a huge debt to Parmenides, Plato, Aristotle, Epicetus, Homer and others?
"Average folks?" Farmers weren't exactly philosophical. Most people couldn't read, and believed the Greek and Roman myths above. They routinely made sacrifices, played sports, attended dramas as religious observances.
Some books:
Everyday Life in Ancient Greece: Nigel Rodgers: 9781780191461: Amazon.com: Books
Amazon.com: Daily Life in the Roman City: Rome, Pompeii, and Ostia (9780806140278): Gregory S. Aldrete: Books
Amazon.com: The Greeks (Penguin History) eBook: H. Kitto: Books