Basically, one may start from being a lay follower (upasaka) and then become a faith follower (saddhanusari), and then become a Dhamma follower (dhammanusari). Finally, this will lead to stream entry.
Of course, a lay follower can become a monk or nun too. That may lead beyond stream entry to higher states of enlightenment including arahatship.
The following sutta talks about being a lay follower (upasaka) of Buddhism:
Once the Blessed One was dwelling among the Sakyas in Nigrodha Park at
Kapilavatthu. There, Mahanama the Sakyan approached the Blessed One.
Having approached and paid respect to the Blessed One, he sat aside.
Then, seated aside, Mahanama the Sakyan said thus to the Blessed One:
"Venerable sir, in what way is one a lay follower (upasaka)?"
"Mahanama, inasmuch as one has gone to the Buddha for refuge, has gone
to the Dhamma for refuge, has gone to the Sangha for refuge; in that
way, Mahanama, one is a lay follower."
"Then, venerable sir, in what way is a lay follower virtuous?"
"Mahanama, inasmuch as a lay follower abstains from destroying living
beings; abstains from taking what is not given; abstains from sexual
misconduct; abstains from lying; and abstains from wine, liquor and
intoxicants that are causes for heedlessness; in that way, Mahanama, a
lay follower is virtuous."
"Then, venerable sir, in what way is a lay follower engaged in his own
welfare, but not in others' welfare?"
"Mahanama, inasmuch as a lay follower is possessed of faith himself,
but rouses not others to possess faith; is possessed of virtue
himself, but rouses not others to possess virtue; is possessed of
liberality himself, but rouses not others to possess liberality; is
himself desirous of meeting with monks, but rouses not others to meet
with monks; is himself desirous of hearing the true Dhamma, but rouses
not others to hear the true Dhamma; is himself habitually mindful of
the Dhamma that is heard, but rouses not others to be mindful of the
Dhamma; has himself ascertained the meaning/benefit of the Dhamma that
is heard, but rouses not others to ascertain the meaning/benefit;
having known the meaning/benefit, having known the Dhamma, is himself
committed to the practice according to the Dhamma, but rouses not
others to be committed to the practice according to the Dhamma; in
that way, Mahanama, a lay follower is engaged in his own welfare, but
not in others' welfare."
"Then, venerable sir, in what way is a lay follower engaged in his own
welfare and in others' welfare?"
"Mahanama, inasmuch as a lay follower is possessed of faith himself,
and rouses others to possess faith; is possessed of virtue himself,
and rouses others to possess virtue; is possessed of liberality
himself, and rouses others to possess liberality; is himself desirous
of meeting with monks, and rouses others to meet with monks; is
himself desirous of hearing the true Dhamma, and rouses others to hear
the true Dhamma; is himself habitually mindful of the Dhamma that is
heard, and rouses others to be mindful of the Dhamma; is himself
ascertained of the meaning/benefit of the Dhamma that is heard, and
rouses others to ascertain the meaning/benefit; having known the
meaning/benefit, having known the Dhamma, is himself committed to the
practice according to the Dhamma, and rouses others to be committed to
the practice according to the Dhamma; in that way, Mahanama, a lay
follower is engaged in his own welfare and in others' welfare."
AN 8.25
All the suttas in the Okkanta Samyutta (SN 25) have the latter stock phrase about faith-followers (saddhānusārī) and Dhamma-followers (dhammānusārī) who may eventually reach stream entry.
So a person may not have achieved any of the four stages of enlightenment starting with stream entry, but at the minimum, he can be consoled that he has come to have conviction and belief in the teachings, thus becoming a faith-follower, and this may eventually lead him to stream entry.
Better yet is someone who has discerned the teachings and understood them to a certain extent, to become a Dhamma-follower. This will then lead him eventually to stream entry. Dhamma-follower is the next stage after faith-follower, but still before stream entry.
"Monks, form is inconstant, changeable, alterable. Feeling...
Perception... Fabrications... Consciousness is inconstant, changeable,
alterable.
"One who has conviction & belief that these phenomena are this way is
called a faith-follower: one who has entered the orderliness of
rightness, entered the plane of people of integrity, transcended the
plane of the run-of-the-mill. He is incapable of doing any deed by
which he might be reborn in hell, in the animal womb, or in the realm
of hungry shades. He is incapable of passing away until he has
realized the fruit of stream-entry.
"One who, after pondering with a modicum of discernment, has accepted
that these phenomena are this way is called a Dhamma-follower: one who
has entered the orderliness of rightness, entered the plane of people
of integrity, transcended the plane of the run-of-the-mill. He is
incapable of doing any deed by which he might be reborn in hell, in
the animal womb, or in the realm of hungry shades. He is incapable of
passing away until he has realized the fruit of stream-entry.
"One who knows and sees that these phenomena are this way is called a
stream-enterer, steadfast, never again destined for states of woe,
headed for self-awakening."
SN 25.10