Sri Krishna gave various instructions in the Gītā befitting the competency or ability of individual souls. He gave advice about karma(the path of performing correct action), jñāna(the path of knowledge), yoga(the path of austerity and meditation) and bhakti(the path of pure devotion). But, if we go through the Gītā thoroughly and carefully, we will find that, ultimately, Krishna takes all to bhakti (devotion).

Krishna first extols the virtues of karma and inspires everyone to engage in it:

na hi kaścit kṣaṇam api
jātu tiṣṭhaty akarma-kṛt
(Bhagavad-gītā, 3.5)

“No one can remain without karma (action) for even a moment.”

niyataṁ kuru karma tvaṁ
karma jyāyo hy akarmaṇaḥ
śarīra-yātrāpi ca te
na prasiddhyed akarmaṇaḥ
(Bhagavad-gītā, 3.8)

“Always perform karma (i.e., nityā-karma, or eternal karma, as enjoined in the scriptures). Doing karma (performing one’s duty) is better than not doing karma(not performing one’s duty), as no one can sustain his or her body without karma (work or action). There are three kinds of karma: karma, akarma and vikarma. Karma is the performance of actions or duties enjoined by the Vedas, akarma is abstinence from actions or duties enjoined by the Vedas and vikarma is the performance of actions or duties prohibited by the Vedas. Actual doers of karma in the world are very rare. Krishna has recommended karma but, ultimately, He is taking us to bhakti:

yajñārthāt karmaṇo ’nyatra
loko ’yaṁ karma-bandhanaḥ
tad-arthaṁ karma kaunteya
mukta-saṅgaḥ samācara
(Bhagavad-gītā, 3.9)

"Perform karma for Yajña.” “Yajña vai viṣṇurti śrute.” In śruti śāstra, Viṣṇu is described as Yajña and one of His names is Yajña. “Yad idaṁ viśvaṁ vyapnotiti viṣṇuḥ”: “Viṣṇu is the all-pervading Supreme Lord, Complete Reality.” If we perform any action for the Supreme Lord, Complete Reality (pūrṇa), we will not fall into bondage. If we perform action for any part, separate from the Whole, we will fall into bondage. “Oṁ tat sat.” The Supreme Lord is tat, transcendental: that which cannot be comprehended by gross and subtle material senses.

We should perform actions for the Supreme Lord without any desire for the fruits of those actions. To perform any action for the Supreme Lord is bhakti, devotion. By inspiring a person to do karma, Krishna takes the karmī (the doer) to bhakti.

When Sri Krishna speaks about jñāna, He extols it thusly:

na hi jñānena sadṛśaṁ
pavitram iha vidyate
tat svayaṁ yoga-saṁsiddhaḥ
kālenātmani vindati
(Bhagavad-gītā, 4.38)

“There is nothing so sanctified as jñāna.”

yathaidhāṁsi samiddho ’gnir
bhasma-sāt kurute ’rjuna
jñānāgniḥ sarva karmāṇi
bhasma-sāt kurute tathā
(Bhagavad-gītā, 4.37)

“As a blazing fire burns wood, reducing it to ashes, so too does jñāna destroy all kinds of karma, reducing it to ashes.” Karma is initiated by the false ego of the doer.

prakṛteḥ kriyamāṇāni
guṇaiḥ karmāṇi sarvaśaḥ
ahaṅkāra-vimūḍhātmākartāham iti manyate
(Bhagavad-gītā, 3.27)

“The jīvās, being enveloped by the illusory energy of the Supreme Lord, which consists of three primal qualities or guṇas [sattvas: goodness, rajas: passion and tamas: ignorance], misunderstand these qualities to be the body and wrongly think themselves to be the doers.”

When sattva-guṇa predominates, we become sāttvika; if rajo-guṇa predominates, rājasika; and, if tamo-guṇa predominates, tāmasika. As per the color of the false ego, karma is also of three colors (white, red and black). The jñānīs (those who practice the path of knowledge) strive for self-realization. So all karma (deluded activity) emerging from the material ego is destroyed by jñāna (proper knowledge). But, by recommending jñāna, Krishna is ultimately taking us to bhakti.

bahūnāṁ janmanām ante
jñānavān māṁ pradadyate
vāsudevaḥ sarvam iti
sa mahātmā su-durlabhaḥ
(Bhagavad-gītā, 7.19)

“After many births, the proponents of jñāna-mārga [the path of knowledge] take absolute shelter of Me, Vāsudeva. Such a saint who sees everything in relation to Vāsudeva is rarely to be found.”

When their knowledge has reached the stage of maturity, jñānīs can understand that no one can know God without His grace. As there is no one equal to or greater than Sri Krishna, no one can attain Him without His grace.

Sri Krishna, Himself, has pronounced a comparative judgment in regard to this in the Gītā:

tapasvibhyo ’dhiko yogi
jñānibhyo ’pi mato ’dhikaḥ
karmibhyaś cādhiko yogi
tasmād yogī bhavārjuna

yoginām api sarveṣāṁ
mad-gatenāntar-ātmanā
śraddhāvān bhajate yo māṁ
sa me yuktatamo mataḥ
(Bhagavad-gītā, 6.46-47)

“O Arjuna! Become a yogī, as a yogī is superior to a hermit who practices severe austerities. The yogī [the worshipper of Paramātmā] is superior to the jñānī [the worshipper of formless Brahman], and is naturally, supremely superior to the karmī [one who performs actions enjoined by the scriptures for mundane benefit]. Among all kinds of yogīs, one who, while concentrating his mind on Me, worships Me—My eternal, transcendental form—with firm faith and devotion is the highest yogī. Hence, the bhakti-yogī is the highest among yogīs.”