I grew up Pentecostal. One of the things I was taught (early and often) was that only believers could receive the Holy Spirit and even then that was a separate step not all believers got to enjoy automatically. Only some got to level up (okay, they never used video game lingo but this was the idea), the ones who prayed long and hard enough and submitted most fully. Everyone else was wandering around without the Spirit to guide or empower them. How sad for them.
Trying to reserve the Spirit for people who have already accepted Jesus (and then gone the extra mile) is a false teaching started by people trying to mark themselves off as more spiritual than others. We inherited their bad teaching and accepted it as given but it’s actually heretical on two fronts: it misunderstands the nature of humans (theological anthropology) and the nature of salvation (soteriology).
First, it is important to understand that the Spirit is actively at work within all humans. God (and God alone) has access to the inner person. This is part of what it means for us to be created in the image of God, to have the breath of God (the Spirit) in our lungs. If the Spirit was totally removed from a human, that human would die. None of us can live completely outside the life of God. Intimate interaction with the Holy Spirit is an intrinsic part of human nature.
Second, the move from unfaith to faith is one that can only be done in the power of the Spirit. None of us comes to salvation unaided by the Holy Spirit. Wesley called this prevenient grace and the idea is rooted in the Bible and the orthodox teaching of the church down through the ages. God calls us first and woos us by the Holy Spirit. We respond and come to faith. Our move is always a secondary move, always a response to what God is already doing. If not, then we are able to save ourselves or earn at least some part of the credit. But that’s not the case. The whole thing is grace that we receive as a gift.
The Holy Spirit is not reserved for those who profess faith in Jesus, much less for some select subset of Christians. The Holy Spirit is with you right now, actively trying to counsel you and lead into wholeness, into life, into grace, into love. Whatever you believe, and where ever you are, stop to listen and receive the Presence that is already as close as the breath in your lungs.