The Entrance chant or song begins the celebration. The Song is to "Foster unity of those who have been gathered, introduce their thoughts to the mystery of the liturgical season..."(n 47).
The song is NOT about welcoming the priest but about ending all the private prayers and conversations, and unifying the community into the celebration. It focuses on God and the celebration.
Songs need to be easily sung by all. The Gathering Song continues as long as needed until the priest and other ministers are in place. Consideration also needs to be given to the song verses, in that the message they are convey may need to go through all the verses and not end at verse 2 or 3 or whenever the priests arrives at his chair.
The Kyrie is ideally a chant to be sung by all the faithful. A trope usually precedes the acclamation, e.g. "Lord Jesus you are Son of God and Son of Mary..."
There are three forms to the penitential rite, make sure the choir and presider know which form is being used. Those forms can be found in the Roman Missal.
"The Gloria is a very ancient and venerable hymn in which the Church gathers together in the Holy Spirit, glorifies and entreats God the Father and the Lamb. The texts of this hymn may NOT [emphasis added] replaced by another text." (n 53)
Ideally this is to be sung, but can be recited.
The Gloria is not used during the seasons of Advent or Lent.