Acts 1:8 (NIV) you will receive power when the Holy Spirit comes
What is the meaning of power ?
I don't know; let's see :
Micah 3:8 But truly I am full of power by the spirit of the LORD, and of judgment, and of might, to declare unto Jacob his transgression, and to Israel his sin.
Since Micah is obviously a prophet, the power of prophecy is one possible meaning; another is being invested with divine authority (might) to judge sins and reprove (declare) transgressions; after all, it takes a certain stamina to stand bravely and uprightly in front of someone, and take them to task for their ill-doings.
Luke 1:17 And he [ John the Baptist ] shall go before him in the spirit and power of Elias, to turn the hearts of the fathers to the children, and the disobedient to the wisdom of the just; to make ready a people prepared for the Lord.
Here, the power of preaching is meant, since it is not a trivial thing to be able to change people's hearts and minds, by convincing them to (successfully) repent of their sins.
Luke 1:35 And the angel answered and said unto her: The Holy Ghost shall come upon thee, and the power of the Highest shall overshadow thee: therefore also that holy thing which shall be born of thee shall be called the Son of God.
Here, God's creative power is intended, to fashion a human body without the aid or assistance of any seed, as with Adam in the Garden of Eden.
Acts 8:18-20 And when Simon saw that through laying on of the apostles' hands the Holy Ghost was given, he offered them money, saying: Give me also this power, that on whomsoever I lay hands, he may receive the Holy Ghost. But Peter said unto him: Thy money perish with thee, because thou hast thought that the gift of God may be purchased with money.
Here, the power to give (rather than merely receive) God's Holy Spirit is being referenced.
Romans 1:3-4 Concerning his Son Jesus Christ our Lord, which was made of the seed of David according to the flesh; and declared to be the Son of God with power, according to the spirit of holiness, by the resurrection from the dead.
Here, the power of life over death is meant, since spirit is related to respiration, (physical) breath being one of the (main) elements of (biological) life.
Romans 15:18-19 For I will not dare to speak of any of those things which Christ hath not wrought by me, to make the Gentiles obedient, by word and deed, through mighty signs and wonders, by the power of the Spirit of God; so that from Jerusalem, and round about unto Illyricum, I have fully preached the gospel of Christ.
Here, the power to perform miracles is explicitly named, alongside the aforementioned power to preach the Gospel and (successfully) capture and convert one's audience.
1 Corinthians 2:4 And my speech and my preaching was not with enticing words of man's wisdom, but in demonstration of the Spirit and of power, that your faith should not stand in the wisdom of men, but in the power of God.
As before, the success of his mission among Gentiles and the Diaspora is attributed to divine intervention, the (humble) apostle of Christ, as Moses before him (Exodus 4:10), deeming his own eloquence insufficient of an explanation for the unexpected spread of the faith.
Ephesians 2:2 In time past ye walked according to the course of this world, according to the prince of the power of the air, the spirit that now worketh in the children of disobedience.
Here, the power of sin and temptation over our human weakness is being spoken of.
2 Timothy 1:7 For God hath not given us the spirit of fear; but of power, and of love, and of a sound mind.
Here, courage is being contrasted with fear.
Is this “power” available for every Christian or was it just for the apostles ?
Were that the case, then why would anyone convert to Christianity in the first place ? For instance, if Christ alone would resurrect (by the power of the Spirit), and those believing in Him not, then why even bother joining His religion, if only a closed circle of select few are privy to the privileges it allegedly provides, as Paul himself argues in 1 Corinthians 15:12-23 ? Similarly for the other things mentioned above.