Assembly Gospel Testimony

Assemblies owe their existance to regular gospel outreach. What does the Bible say about an assembly's part in the Great Commision?
 

Mark 16:15
15. And he said unto them, Go ye into all the world, and preach the gospel to every creature. 16He that believeth and is baptized shall be saved; but he that believeth not shall be damned.

Matthew 28

16. Then the eleven disciples went away into Galilee, into a mountain where Jesus had appointed them. 17. And when they saw him, they worshipped him: but some doubted. 18. And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth. 19. Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: 20. Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.

Acts 1

6. When they therefore were come together, they asked of him, saying, Lord, wilt thou at this time restore again the kingdom to Israel? 7. And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power. 8 But ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth