Three-step doctrine, as I understand it, is the belief that saving faith is not accomplished until Repentance, Water Baptism, and the Baptism of the Holy Ghost with the evidence of speaking in other tongues and it takes these three steps before the blood can be applied or new birth can take place.
I think a good place to start would be a general overview of the support for the three-step doctrine.
Pro:
Support for this doctrine is found in;
Acts 2:38
38And Peter said to them,(A) "Repent and(B) be baptized every one of you(C) in the name of Jesus Christ(D) for the forgiveness of your sins, and you will receive(E) the gift of the Holy Spirit.
John 3:5
John 3:3-8 (English Standard Version)
3Jesus answered him, "Truly, truly, I say to you, unless one is(A) born(B) again[a] he cannot(C) see the kingdom of God." 4Nicodemus said to him, "How can a man be born when he is old? Can he enter a second time into his mother’s womb and be born?" 5Jesus answered, "Truly, truly, I say to you, unless one is born(D) of water and the Spirit, he cannot enter the kingdom of God. 6(E) That which is born of the flesh is(F) flesh, and that which is born of the Spirit is spirit.[b] 7(G) Do not marvel that I said to you, 'You[c] must be born(H) again.' 8(I) The wind[d] blows(J) where it wishes, and you hear its sound, but you do not know where it comes from or where it goes. So it is with everyone who is born of the Spirit."
These are the first that come to my mind. If anyone can give more support by posting scriptures please do so.