Note this scripture:
Acts 2: 4 And they were all
filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
It says they were filled with the HG.
So let me ask you this, were the ones in the upper room not saved before the HG filled them?
Was there no spirit in their hearts while they tarried for 120 days, praying? Why would they even be there if the spirit of the Lord was not there convicting them, and causing them to seek Him? Why would you spend 4 months in one room praying if there was no spirit at work?
Here's another illustration. I can have a cup that is halfway full, I can still drink from it and enjoy it, but it's not enough, and its not satisfying because I don't have all the fullness available yet to me, because the cup is half empty. When the cup is filled, I can drink from the fullness of the cup, and enjoy all of it, more of it, and be satisfied. The ingredients in the cup didn't change, but the amount did, and the fullness satisfied me, where as the half empty glass was not enough to satisfy me.
In the same way, the spirit of the Lord in a measure comes to us, drawing us to Him, and we cry out to Him in repentance and complete our obedience in baptism and then the Lord is there to fill our cup to overflowing with the fullness of the spirit available to us, with giftings, signs and wonders, as He chooses to give.