We have to surrender ourselves completely to the Lord with faith and devotion in Him, serve others to the best of our capacity, and never be a source of sorrow to anybody.
Certainly you will have doubts. There will be questionings and faith will return again. That is how faith is established.
Is faith so cheap, my child? Faith is the last word. If one has faith, the goal is practically reached.
Does one get faith by mere studying of books? Too much reading creates confusion. The Master used to say that one should learn from the scriptures that God alone is real and the world illusory.