The handbook says the devotional outlook of the Legion is based on faith.
Faith is important. Pope Benedict says, "Belief in Jesus Christ is the way to arrive definitively at salvation".
When Jesus was pleased with someone He would praise their faith. He said it was their faith that enabled Him to cure them. When He was displeased, He would say, "You of little faith". Jesus attributes failure to a lack of faith. Matthew 17:20
Jesus says that if we have faith we can accomplish great things like moving mountains. Matthew 17:20
Our faith is spread by evangelization. Recent popes have spoken of a New Evangelization. In the past, evangelization was done by missionaries working in places like Africa. Today the need for evangelization is in formerly Christian countries where many have fallen away and are unaware of the Catholic faith. The New Evangelization involves all Catholics spreading the faith to their friends and neighbors.
Your faith, like hope and love is increased when it is given away. When you give the gift of faith to someone, your own faith increases.
In doing our Legion work, spreading the faith, giving people hope, and loving them, we increase our own faith, hope and charity.