What Is The Meaning Of Life? Why Did God Create Us In The First Place? What Are We To Do?

He Plainly GivesUs His Answer To Those Questions In THE REVELATIONS ...

"Thou art worthy, O Lord, to receive glory and honour and power: for thou hast created all things, and for thy pleasure they are and were created." Rev.4:11.

He Created us, and the Universe, for His pleasure... to do His pleasure... with a free will choice.  

"Now therefore make confession unto the Lord God of your fathers, and do his pleasure...." Ezre 10:11

He is the very essence of Uprightness and tests us to please Him by walking in His uprightness:     

"I know also, my God, that thou triest the heart, and hast pleasure in uprightness." 1 Chron.29:17

Our Heavenly Father has pleasure in our prosperity:

"...Let the Lord be magnified, which hath pleasure in the prosperity of his servant." Psm.35:27.

He takes pleasure in our fear=('yare'=reverence), and our hope in His mercy:
The Lord taketh pleasure in them that fear him, in those that hope in his mercy." Psm. 147:11.

Our LORD takes pleasure in us ... his people and in beautifying believers with His salvation:

"For the Lord taketh pleasure in his people: he will beautify the meek with salvation." Psm. 149:4.

The only pleasure God takes in the wicked is that they turn to Him, away from sin, to eternal life:

"As I live, saith the Lord God, I have no pleasure in the death of the wicked; but that the wicked turn from his way and live.... Ezek.33:11.

God has no pleasure in the physical death of the spiritually dead: His pleasure is in their turning and living.

"For I have no pleasure in the death of him that dieth, saith the Lord God: wherefore turn yourselves , and live...." Ezek. 18:32. 

Our Heavenly Father had pleasure in removing His Kingdom of "Salvation Nation" from the Jews and giving it to the followers of his Son Jesus Christ... Savior and King of Christians.

"Fear not, little flock; for it is your Father's good pleasure to give you the kingdom." Luke 12:32.

All of this was and is the perfect will and good pleasure of God when He grafted believing Gentiles into the Jewish olive tree as His "adopted" children through Jesus (Rom.11:17-24):

"Having predestinated us unto the adoption of children by Jesus Christ to himself, according to the good pleasure of his will...." Eph.1:5.

And that is the answer to the "mystery of his will" which is His "good pleasure that He has "purposed in himself".

"Having made known unto us the mystery of his will, according to his good pleasure which he hath purposed in himself...." Eph.1:9.

And ... so.. now, God is working in us, His Churches, Born Again Christians, whether Jew or Gentile, who are Christ's Salvation Nation as recorded in the New Testament, "to do of his good pleasure" in fulfilling all of the above.

"For it is God which worketh in you both to will and to do of his good pleasure." Phil.2:13.