The beginning of the good news of Jesus Christ, the Son of God.Work with me here:
"Good news" was a common expression in the ancient world. Most often was used in military contexts, to report victory in battle. When a general or emperor was told there was "good news," they immediately knew the army had won.
But "good news" was also used to describe important events in the lives of the top people of the Roman empire. For example, the birthday of Caesar Augustus was always announced as, "good news for the world," since Caesar was ruler of the world known to them at the time.
The ancient term "good news" was always plural. The good news of Augustus's birthday was the announcement of one good tiding among others. But Mark uses "good news" in the singular, making sure his readers knew that the advent of Jesus in the world was not simply one fine thing among many good things. It is a stupendous, exceptional event that is unique and unequaled.
This rhetorical device was intended to evoke a belief and understanding in the minds of the hearers of the Gospel. It was intended to make them perk up and take notice.
One way to understand the meaning of Mark's word is this:
"The beginning of the victory of Jesus Christ, the Son of God."
"Christ" is Greek for, "anointed one." But the Greeks didn't use the word in association with their gods whom they believed lived on Mount Olympus. So Jesus the anointed one, the Son of God, would not have made much sense to a Greek.
However, in the Old Testament there are references to the priests being anointed, repetitive references to kings of Israel being anointed, and also some prophets. There is even a description in Isaiah of the Persian King Cyrus being anointed. In most of these contexts, the anointed one is described as one to whom God gives victory.
"The beginning of the victory of Jesus the Triumphant, Anointed One of God, the Son of God."
I think that gets more accurately to the sense of what Mark was trying to convey.