True. There is nothing we can do on our own which will gain us immortality or eternal life. We could have all the faith in the world that we will be saved and do many billion good works and without Jesus Christ we would not be saved.There is nothing we can do on our own to "earn" salvation. It is a free gift of grace. Without Christ we are utterly condemned.
But does this mean that faith and good works should be cast out the window? NO! Even though our own faith and good works are not the saving force behind salvation, God does require that we do good works and have faith.
Matthew 7:21
Not every one that saith unto me, Lord, Lord, shall enter into the kingdom of heaven; but he that doeth the will of my Father which is in heaven.
This does not mean that doing the will of our Father in heaven gains or buys us salvation but that it is a requirement of God before Jesus will grant us salvation into the kingdom of heaven. Jesus is the salvation. Faith and works are a requirement by Jesus before he grants his salvation upon us.
Ephesians 2:8-10
8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God:
9 Not of works, lest any man should boast.
10 For we are his workmanship, created in Christ Jesus unto good works, which God hath before ordained that we should walk in them.
This verse clearly teaches that it is the grace of God by which we are saved. It is not by our works that we are saved. Nor is it by faith that we are saved even though it is through faith that we can come to that saving grace. And a true faith is dead without good works. So yes! It is only by the grace of God that we are saved! But, God requires us to do good works and has ordained that we should walk in them. Our works and faith don't do the saving but are required before the saving grace of Jesus Christ may be granted. The verse above actually delineates between what is required of us and what actually does the saving of our souls. God desires us to be good beings and to do good to one another. Those actions don't save us but they are necessary for us to qualify to receive the grace that will give us entrance into his kingdom.