jNAna has three stages.
PuruShottamachAryA lists three stages of jNAna. These are ShravaNa (hearing the texts), manana (reflection and discussion) and nidhidhyAsana (vision of the lord). This is based on bRRihadAraNyakaupaniShad (2.4.5):
mantavyo nididhyAsitavyo maitreyi, Atmano vA are darshanena shravaNena matyA vij~nAnenedaM sarvaM viditam
The Self, my dear Maitreyī, should be realised—should be heard of, reflected on and meditated upon. By the realisation of the Self, my dear, through hearing, reflection and meditation, all this is known.
and shA~NkhAyanAraNyaka (13.1):
tad u ha vAtmA draShTavyaH shrotavyo mantavyo nididhyAsitavya iti
ViShNupurANa 6.5.61, 65 also gives a description of the stages or types of knowledge. I think that this classification can be combined with the one I have explained above. It includes the distinction between hearing, reflecting and attaining vision, so it confirms the position of PuruShottamachAryA.
AgamotthaM vivekAch cha dvidhA j~nAnaM tathochyate, shabdabrahmAgamamayaM paraM brahma vivekajam. dve vidye veditavye vai iti chAtharvaNI shrutiH, parayA tv akSharaprAptir RRigvedAdimayAparA.
Knowledge is of two kinds, that which is derived from scripture [ShravaNa], and that which is derived from reflection [manana]... The Atharva Veda also states that there are two kinds of knowledge; by the one, which is the supreme, god is attained [nidhidhyAsana]; the other is that which consists of the Rig and other Vedas [ShravaNa and manana].
When kRRiShna gave jNAna to arjuna (gIta 18.64), he said
shRRiNu me paramaM vachaH... tato vakShyAmi te hitam
Hear this supreme instruction from me, for it is for your benefit
GIta also says (13.26):
shrutvAnyebhya upAsate te ’pi chAtitaranty eva mRRityuM shruti-parAyaNAH
By hearing from others, they begin to worship: because they are inclined to the process of hearing, they also certainly overcome death.
GIta 10.18 also gives a good example of how we should desire to listen for attaining jNAna. On manana, muNDaka upaniSad (3.2.6) says about liberated souls:
Having without doubt well ascertained the significance of the knowledge of Vedanta
NidhydhyAsana, also called brahmavidya, has 32 types according to upaniSads
As well as these three stages of jNAna itself, there are certain qualifications or conditions for attaining it. You can read about the nimbArka description of them here. Not all of them are absolutely necessary: one can begin jNAna by just one of them. Following our obligatory actions (according to our state in life and dharmasUtra) is an auxiliary, so brahmasUtra (3.4.26) summarises bRRihadAraNyakaupaniShad (4.4.22) which says that
tametaM vedAnuvachanena brAhmaNA vividiShanti yaj~nena dAnena tapasA.anAshakena; etameva viditvA munirbhavati
The Brahmanas seek to know It through the study of the Vedas, sacrifices, charity, and austerity consisting in a dispassionate enjoyment of sense-objects.
shA~NkhAyanAraNyaka (13.1) teaches:
tam etaM vedAnuvachanena vividiShanti brahmacharyeNa tapasA shraddhayA yaj~nenAnAshakena cheti mANDUkeyaH
Udogyaparva (43.8 f.) of the mahAbhArata confirms that:
apa se j~nAna kI prApti va j~nAna se AtmA kI prApti kA kathana (I'm not sure about finding the complete text)
It is for attaining to that Supreme Soul that asceticism and sacrifices are ordained, and it is by these two that the man of learning earneth virtue. Destroying sin by virtue, his soul is enlightened by knowledge. The man of knowledge, by the aid of knowledge, attaineth to the Supreme Soul.
In describing the personal qualities needed to begin jNAna, shvetAshvatarupaniShad (6.22-23) says
nAprashAntAya dAtavyaM nAputrAyAshiShyAya vA punaH. yasya deve parA bhaktir yathA deve tathA gurau, tasyaite kathitA hy,
[Vedanta] should not be given to one not tranquil, nor again to one who is not a son or a pupil. To him who has bhakti for God, and for his guru as for God, have these matters been declared.
So, Vedanta and jNAna can only be given by a spiritual father (guru), or bodily father. Bhakti is a requirement for it. BrahmasUtra 3.4.27 summarises how bRRihadAraNyakaupaniShad (4.4.23) gives some more conditions for beginning jNAna marga:
tasmAdevaMvichChAnto dAnta uparatastitikshuH samAhito bhUtvAtmanyevAtmAnaM pashyati
he who... having become calm, self-restrained, indifferent, patient and collected, should see the self in the self alone
Devotional service is also an auxiliary to jNAna, especially for those without varna.
In conclusion, there are three auxiliaries to jNAna marga: three or six obligations (depending on varna), eight personal qualities (tranquil, bhakti, son or pupil, calm, self-restrained, indifferent, patient and collected), and six general requirements (devotional service in its many forms, deep learning, childlike simplicity, unostentatiousness, profound thoughtfulness and silence). In total this leaves 17 or 20 part auxiliaries to jNAna marga. The three stages are hearing, reflection and vision of the lord.
YogavAsiShTha 3.118 is a secondary text which describes seven stages of knowledge. The whole chapter defines these stages, and these verses 5-6 are a simple list of them.
j~nAnabhUmiH shubhechChAkhyA prathamA samudAhRRitA,
vichAraNA dvitIyA tu tRRitIyA tanumAnasA.
padArthAbhAvanI ShaShThI saptamI turyagA smRRitA.
The grounds of knowledge comprise the desire of becoming good said subhechha, and this good will is the first step. Then comes discretion or reasoning (vicharana) the second, followed by purity of mind (tanu-manasa), which is the third grade to the gaining of knowledge. The fourth is self reliance as the true refuge said: Satta-patti, then asansakti or worldly apathy as the fifth. The sixth is padarthabhava or the power of abstraction, and the seventh or the last stage of knowledge is turya-gati or generalization of all in one.