One need not be a religious scholar or perfect person, but faith and practice is necessary.
Neither hell nor a purgatory is a place apart from the present moment. These are lifestates, not different places. Even faith as tiny as a mustard seed has the potential to grow into salvation with practice. Calling forth faith and practice even in a hellish state, an animal state or a state of anger or even a heavenly state of rapture or theoretical awakening, can lead to the stage of non-retrogression, where, no matter the degrees of hell and suffering, or animality, if strong faith and practice is maintained, one can reach the stage of non-retrogression.
By analogy a person learning to drive a car only in an empty parking lot, is not yet ready for difficulty of driving on a speeding highway. One must be tested against adversity.
Otherwise the term “purgatory,” is just a term with expedient meaning.