Acts 11:17 Therefore if God gave them the same gift as he also gave us after believing in the Lord Jesus Christ, who was I to hinder God?” 11:18 When they heard this, they ceased their objections and praised God, saying, “So then, God has granted the repentance that leads to life even to the Gentiles.”
Romans 5:11 Not only this, but we also rejoice in God through our Lord Jesus Christ, through whom we have now received this reconciliation.
5:15 But the gracious gift is not like the transgression. For if the many died through the transgression of the one man, how much more did the grace of God and the gift by the grace of the one man Jesus Christ multiply to the many! 5:16 And the gift is not like the one who sinned. For judgment, resulting from the one transgression, led to condemnation, but the gracious gift from the many failures led to justification. 5:17 For if, by the transgression of the one man, death reigned through the one, how much more will those who receive the abundance of grace and of the gift of righteousness reign in life through the one, Jesus Christ!
Romans 6:23 For the payoff of sin is death, but the gift of God is eternal life in Christ Jesus our Lord.
Ephesians 2:8 For by grace you are saved through faith, and this is not from yourselves, it is the gift of God; 2:9 it is not from works, so that no one can boast.
1 Peter 3:7 Husbands, in the same way, treat your wives with consideration as the weaker partners and show them honor as fellow heirs of the grace of life. In this way nothing will hinder your prayers.
John 3:14 Just as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up, 3:15 so that everyone who believes in him may have eternal life.”
3:16 For this is the way God loved the world: He gave his one and only Son, so that everyone who believes in him will not perish but have eternal life. 3:17 For God did not send his Son into the world to condemn the world, but that the world should be saved through him. 3:18 The one who believes in him is not condemned. The one who does not believe has been condemned already, because he has not believed in the name of the one and only Son of God.
We see that there is a gift from God which is multi-faceted. From the context of these occurrences of "the gift", it does seem to be discussing various aspects of one gift, not many different gifts. This is not to be confused with the gifts (plural) of the Holy Spirit to those He indwells, but is instead what we accept and receive when we trust Jesus alone for our salvation.
In accepting this gift we receive righteousness, eternal life, salvation. Acts 11:17-18 refers to the gift as being the Holy Spirit, which they received "after they believed", so believing is how they "asked" and the Spirit is what they received. There is also the gift of "repentance to life" in that same section. In Romans we learn that we can receive "the gift of righteousness" by faith in Jesus Christ, which means that we become instantly justified (cleared of all charges against us and thus reconciled to God) by means of his sacrifice. We also are given "eternal life" in him. In Ephesians we are told that salvation by faith instead of works is "the gift of God". And in Peter, we are assured that this "grace of life" is not just for half the human race!
Along with the study showing that Jesus is God in the flesh who died for the sins of all mankind, we see here that this credit is not applied to our account until we accept it as a gift. But we must define exactly what it is we must believe in order to receive it.
Some claim that all we need is to believe in some vague "Jesus", never knowing which "Jesus" he is or why and how he can get us into heaven. But Jesus Himself clearly stated that we must believe in him and the One who sent him (John 12:44, 17:21), namely YHWH (Jehovah), the One True God. To accept one and not the other is not saving faith. So we must accept that Jesus is God in the flesh, because only God could ever pay for our sins. This is what justification is all about: Jesus paid the penalty for the sin that was keeping us separated from God, reconciling to Him those who accept his payment on their behalf.
Although eternal life is part of the gift, some say it's the ONLY part, the only thing we must believe to be saved. There are two problems with that view: it confuses the gift with how we receive it, and even if the two were synonymous it is not the whole gift. Besides, if we had to have this assurance of eternal life before we could actually get it, why did the apostle John write a whole letter for the purpose of giving such assurance to those who already believed (1 John 5:13)?
The bottom line is this: Jesus offers us a gift that includes eternal life in heaven, instant justification in God's eyes, bringing reconciliation between the believer and God, and the Holy Spirit as a "deposit guaranteeing our inheritance". That defines The Gift. But we receive The Gift by accepting Jesus for who he claimed to be: God in the flesh, who alone could ever pay for our sins, who did so by dying on the cross in our place, then raising himself up to life again. This is the full and only gospel message preached throughout the New Testament.