Answer
The Lord has divided all spiritual paths in the Bhagavad Gita into two principal categories — the path of Pravritti (the householder's 'Yoga' path, the path of Karma Yoga) and the path of Nivritti (the path of Sannyasa, or the 'Sankhya' path).
Dhyana Yoga and Jnana Yoga are principally suited for sannyasis (renunciants).
The technical meaning of Dhyana Yoga is meditation upon the formless God and the formless Atman.
Jnana Yoga, too, in its pure form, is the worship of the formless Brahman — it sees oneness between the individual soul and Brahman and regards the world as illusory.
However, dhyana (meditation) and jnana (knowledge) also have a practical meaning that is applicable in the householder's life — meditation upon the saguna (personal) form of God, and jnana in the form of self-reflection.
Samanvaya Yoga — The Supreme Path for the Householder
Some people follow only Bhakti Yoga, some only Karma Yoga, and some only Jnana Yoga; but the view of the Bhagavad Gita is one of synthesis — harmonizing all of these.
This has been called Samanvaya Yoga — or one may say, Pari-Upasana Yoga, because when the worship of God is performed in every way, in its complete fullness, it is called 'pari-upasana' (all-encompassing worship).
The Path of Karma for the Householder
In the householder's life, one must certainly become a Karma Yogi, because worldly duties have to be performed.
But if those selfless and desireless actions are infused with the spirit of devotion, illumined by knowledge, and accompanied by some meditation on the saguna form of God along with continuous mental chanting (manasa-japa), then this way of life becomes the most excellent. This is the balanced diet of spirituality.
And just as a balanced diet reduces bodily diseases, so too does a balanced yogic diet cure the ailments of the mind and strengthen the soul.
See how, in the following verses, the Lord asks one to infuse Karma Yoga with the element of meditation:
Ye tu sarvani karmani mayi sannyasya matparah | Ananyenaiva yogena mam dhyayanta upasate || Tesham aham samuddharta mrityu-samsara-sagarat || 12:6-7
'Those who, surrendering all actions to Me, worship Me with unwavering meditation — I deliver them from the ocean of mortal samsara.'
The Lord's Message of Synthesis
The Lord has repeatedly declared that the wise devotee is exceedingly dear to Him.
Tesham jnani nitya-yukta eka-bhaktir vishishyate | Priyo hi jnanino'tyartham aham sa cha mama priyah || 7:17
'Among them, the wise one who is ever steadfast and devoted exclusively is the most excellent; I am supremely dear to the jnani, and he is supremely dear to Me.'
And in the twelfth chapter, the Lord, describing each noble virtue one by one, has declared repeatedly — 'Such a devotee is dear to Me.'
Adveshta sarva-bhutanam maitrah karuna eva cha... Yo mad-bhaktah sa me priyah || 12:13-14
In the same manner, while teaching nishkama-karma (desireless action) and anasakti-yoga (the yoga of non-attachment) infused with jnana and bhakti, the Lord has firmly recommended Karma Yoga.
Karmanye vadhikaraste ma phaleshu kadachana. 'Your right is to action alone, never to its fruits.' 2:47
Conclusion
Thus, a householder should make a proper synthesis of all these elements — Karma, Bhakti, and Jnana. It is through their harmonious integration that one's life becomes complete and God-oriented.
As for the questions — what exactly is Jnana, what is Bhakti, and what are their characteristics — these are subjects of elaboration, and they can be discussed separately.
For now, it suffices to say that Samanvaya Yoga is the most excellent path of spiritual practice for a householder.