Mark 1

Mark began his record -

"THE beginning of the gospel of Jesus Christ, the Son of God..." (New Testament | Mark 1:1)

In my mind, this does not suggest the beginning of the preaching of the gospel for the gospel was had in the days of Adam. But it is the beginning of the mortal ministry and atonement that fulfills the gospel plan. In modern day, the Lord declared -

"...this is my gospel—repentance and baptism by water, and then cometh the baptism of fire and the Holy Ghost, even the Comforter, which showeth all things, and teacheth the peaceable things of the kingdom." (Doctrine and Covenants | Section 39:6)

In preface to that commandment, the Savior made it clear the conditions of His gospel -

"...verily, verily, I say unto you, he that receiveth my gospel receiveth me; and he that receiveth not my gospel receiveth not me." (Doctrine and Covenants | Section 39:5)

But there is another aspect with the meaning "beginning" as testified by Mark. He went on to describe the baptism by water, and the baptism of fire and the Holy Ghost of the Savior which would again suggest that this is the beginning of His gospel - repentance, baptism, and receiving the Holy Ghost. This is the gate. There is much more -

"Wherefore, ye must press forward with a steadfastness in Christ, having a perfect brightness of hope, and a love of God and of all men. Wherefore, if ye shall press forward, feasting upon the word of Christ, and endure to the end, behold, thus saith the Father: Ye shall have eternal life." (Book of Mormon | 2 Nephi 31:20)

Beginning would only suggest initial saving ordinances where there are others to adminstered based upon faithfulness.