Early Christianity was incredibly diverse. Edward Gibbon (The Decline and Fall of the Roman Empire) estimates that there were at least fifty Christian sects by the second century.
With so much diversity, it is difficult to give a short statement of the beliefs of "an early Christian". Some seem to have believed that Jesus was a heavenly High Priest, but perhaps not a person who had recently lived on earth. Whether or not Paul believed that Jesus had lived on earth is unclear to some, but he does not seem to have believed that Jesus had lived and died in the recent past. Some even believed that the merciful and loving God of Christianity was not the harsh and unforgiving God of the Jews, whom they called the Demiurge.
It seems that the concept of the Trinity had not yet evolved by the end of the first century CE. Many Christian doctrines really only matured under the rule of the Roman Emperor Constantine, in the fourth century. Constantine himself is said to have delayed his baptism until his deathbed in the belief that baptism washed away all one's past sins, but that one could only be baptised once - he wanted the freedom to commit sins as long as possible.
Early Christians believed in Jesus and that he would return again to Earth. They also believed that God would be there when they died and they would get into the kingdom of heaven after life and have eternal life with God. This was good news to the Christians and that is why they were prepared to die for their beliefs