(And, even more so, when they are Not affiliated to any particular church.)
Nowadays: the only Christians are discerning Christians.
(As of 2023 and in The West; un-discerning obedience to church - to any church - is a fast-track to subversion, corruption, inversion - and damnation.)
This discernment implicitly depends on a distinction between "Christianity" and "The Church" - and this is true whichever church is being followed.
Sometimes, this distinction is explained in terms of the Mystical church versus Institutional church; yet, this concept also implies that Christianity is something different from the here-and-now actuality of any particular church.
Such discernment is evident whenever church instructions/ teaching/ interpretations etc. are disobeyed/ ignored/ explained-away for principled Christian reasons.
But not many Christians realize that in doing this very necessary discernment, they are - mostly implicitly - asserting that real Christianity is significantly distinct from the church. And, because implicit, this process is largely unconscious; and because unconscious, the implications tend to be missed - and discernment is only half-hearted. This often leads into a kind of sleep-walking toward damnation. That is; to changing sides in the spiritual war of this world, and supporting the side that rules much of the world (and all of The West), and is against God and divine Creation.
Therefore; it seems of vital importance that Christians distinguish consciously and explicitly between Christianity and "The Church" - and this necessity applies whatever "The Church" is for that person.
Once such a distinction has been acknowledged, then a process can begin in which a clearer and more accurate understanding of Christianity can develop.
Because, typically, a great deal of what Christians initially regard as Christianity is not so; but is instead contradictory, or superfluous, or historically contingent.
Developing this vital understanding of Christianity begins with whatever sources a person has already encountered: for instance; Scripture, tradition, church teachings, theology, philosophy, devotional sermons and books etc etc...
There is no prior-evident limit to what might turn-out to be of value in clarifying the true nature of Christianity. So there will probably begin some kind of quest for understanding, and this may lead to novel sources.
I would guess that convenient availability of sources is one factor, and that (over time, given willingness and intent) this will be shaped by divine providence.
What is being sought is the true reality of Christianity distinct from any particular source of external knowledge - and the tools of the quest may be summarized as our intuitive evaluations plus the Holy Ghost-guided ability directly to know truth (given correct motivations); supported by our innate ability to recognize and value coherence, and to discard incoherence.
As I said above; I think all real Christians are at least part-way along this path - but have not accepted the full implications of what they are already-doing by living in accordance with their (very necessary) discernments.
They simply need to be honest, clear and explicit about what they are already-doing; and follow it through to the necessary and desirable conclusions...
Whatever these conclusions may turn-out to be.