Most of the Mass Propers are quite complicated and too difficult for beginners to sing. This is especially true of the Gradualia. Exceptions are some of the Introits, such as the easy "Gaudeamus" texts sung on several occasions including the Feast of All Saints, and some of the Communion verses.
The usual way round this is to sing the Propers to psalm tones. This is reasonably straightforward provided that the settings follow the punctuations. It is essential to chose the psalm tone that is in the same mode as the official setting. This is shown as a small figure at the top of each text. The modes for each Proper have been carefully selected to suit the mood of the particular day's feast or other celebration and should be adhered to. They will also then link correctly to psalm verses in the Introits or to the Alleluia for the day or season.
Seasonal Alleluia settings such as that for Christmas and Easter are worth learning but simple alleluia settings to use with each of the psalm tone chants are given towards the front of the Liber Usualis.