How important is it to have faith? Considering the fact that it is one of the gifts of the Spirit, it is very important and something we should all desire to have.
Scripture tells us that we cannot hope to please God without faith. It is impossible to even come to God without believing He exists (Hebrews 11:6). So, God is pleased by our faith. Jesus demonstrated this when He responded to the faith of the centurion who believed that Jesus could heal his sick servant but just giving the word. Jesus' response to the "great faith" of the centurion (Matthew 8:10) clearly shows that He was pleased.
Faith can accomplish much in the life of the believer. James 5:15 tells us that the prayer of faith can not only heal the sick, but also forgive sins. Throughout Jesus' earthly ministry, we see many examples of people receiving healing and forgiveness through Jesus simply because of their faith.
In Mark 11:22-24, Jesus taught that faith can give us the ability to move mountains. When facing a difficult situation in your life, one that appears to be as unmovable as a mountain, prayers offered in faith will bring an answer from God. Through faith, that mountain will be moved. Faith is also one part of the whole armor of God by which we can secure victory in our spiritual battles. Ephesians 6:16 describes faith as a shield by which we can deflect all that the enemy of our souls throws at us.
Finally, and most importantly, faith is what we need for salvation. It is by God's amazing grace given through our faith in Jesus that we are saved (Ephesians 2:8). The Lord's promise to us in John 3:16 is that, because God loves us so much, when we believe in Jesus--when we put our faith in Him--we will not perish but will have eternal life. And that is the best reason of all to have faith!