If the Holy Spirit is essential for salvation,
Answer: Acts 28:27-29 (King James Version)
27For the heart of this people is waxed gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.
28Be it known therefore unto you, that the salvation of God is sent unto the Gentiles, and that they will hear it.
29And when he had said these words, the Jews departed, and had great reasoning among themselves.
must one work miracles or speak in "languages" to be saved?
Answer: NO.
2 Corinthians 6
1We then, as workers together with him, beseech you also that ye receive not the grace of God in vain.
2(For he saith, I have heard thee in a time accepted, and in the day of salvation have I succoured thee: behold, now is the accepted time; behold, now is the day of salvation.)
3Giving no offence in any thing, that the ministry be not blamed:
4But in all things approving ourselves as the ministers of God, in much patience, in afflictions, in necessities, in distresses,
5In stripes, in imprisonments, in tumults, in labours, in watchings, in fastings;
6By pureness, by knowledge, by long suffering, by kindness, by the Holy Ghost, by love unfeigned,
7By the word of truth, by the power of God, by the armour of righteousness on the right hand and on the left,
8By honour and dishonour, by evil report and good report: as deceivers, and yet true;
9As unknown, and yet well known; as dying, and, behold, we live; as chastened, and not killed;
10As sorrowful, yet alway rejoicing; as poor, yet making many rich; as having nothing, and yet possessing all things.
11O ye Corinthians, our mouth is open unto you, our heart is enlarged.
12Ye are not straitened in us, but ye are straitened in your own bowels.
13Now for a recompence in the same, (I speak as unto my children,) be ye also enlarged.
14Be ye not unequally yoked together with unbelievers: for what fellowship hath righteousness with unrighteousness? and what communion hath light with darkness?
15And what concord hath Christ with Belial? or what part hath he that believeth with an infidel?
16And what agreement hath the temple of God with idols? for ye are the temple of the living God; as God hath said, I will dwell in them, and walk in them; and I will be their God, and they shall be my people.
17Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you.
18And will be a Father unto you, and ye shall be my sons and daughters, saith the Lord Almighty.
or, does it influence gradually like Jesus said in John 3:7:
Answer: Your Statement about John 3:7 is False and is not supported by the Holy Scripture.
John 3
1There was a man of the Pharisees, named Nicodemus, a ruler of the Jews:
2The same came to Jesus by night, and said unto him, Rabbi, we know that thou art a teacher come from God: for no man can do these miracles that thou doest, except God be with him.
3Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
4Nicodemus saith unto him, How can a man be born when he is old? can he enter the second time into his mother's womb, and be born?
5Jesus answered, Verily, verily, I say unto thee, Except a man be born of water and of the Spirit, he cannot enter into the kingdom of God.
6That which is born of the flesh is flesh; and that which is born of the Spirit is spirit.
7Marvel not that I said unto thee, Ye must be born again.
8The wind bloweth where it listeth, and thou hearest the sound thereof, but canst not tell whence it cometh, and whither it goeth: so is every one that is born of the Spirit.
9Nicodemus answered and said unto him, How can these things be?
10Jesus answered and said unto him, Art thou a master of Israel, and knowest not these things?
11Verily, verily, I say unto thee, We speak that we do know, and testify that we have seen; and ye receive not our witness.
12If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things?
13And no man hath ascended up to heaven, but he that came down from heaven, even the Son of man which is in heaven.
14And as Moses lifted up the serpent in the wilderness, even so must the Son of man be lifted up:
15That whosoever believeth in him should not perish, but have eternal life.
16For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life.
17For God sent not his Son into the world to condemn the world; but that the world through him might be saved.
18He that believeth on him is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God.
19And this is the condemnation, that light is come into the world, and men loved darkness rather than light, because their deeds were evil.
20For every one that doeth evil hateth the light, neither cometh to the light, lest his deeds should be reproved.
21But he that doeth truth cometh to the light, that his deeds may be made manifest, that they are wrought in God.
22After these things came Jesus and his disciples into the land of Judaea; and there he tarried with them, and baptized.
23And John also was baptizing in Aenon near to Salim, because there was much water there: and they came, and were baptized.
24For John was not yet cast into prison.
25Then there arose a question between some of John's disciples and the Jews about purifying.
26And they came unto John, and said unto him, Rabbi, he that was with thee beyond Jordan, to whom thou barest witness, behold, the same baptizeth, and all men come to him.
27John answered and said, A man can receive nothing, except it be given him from heaven.
28Ye yourselves bear me witness, that I said, I am not the Christ, but that I am sent before him.
29He that hath the bride is the bridegroom: but the friend of the bridegroom, which standeth and heareth him, rejoiceth greatly because of the bridegroom's voice: this my joy therefore is fulfilled.
30He must increase, but I must decrease.
31He that cometh from above is above all: he that is of the earth is earthly, and speaketh of the earth: he that cometh from heaven is above all.
32And what he hath seen and heard, that he testifieth; and no man receiveth his testimony.
33He that hath received his testimony hath set to his seal that God is true.
34For he whom God hath sent speaketh the words of God: for God giveth not the Spirit by measure unto him.
35The Father loveth the Son, and hath given all things into his hand.
36He that believeth on the Son hath everlasting life: and he that believeth not the Son shall not see life; but the wrath of God abideth on him.