In plain words
Nourish the devas through this, and may the devas nourish you. Nourishing one another, you shall attain the highest good.
Word for word
Nourish the devas by this; may those devas nourish you; nourishing one another, you shall attain the highest good.
The commentators
Bhagavadgītābhāṣyam
कथम् —
देवान् इन्द्रादीन् भावयत वर्धयत अनेन यज्ञेन । ते देवा भावयन्तु आप्याययन्तु वृष्ट्यादिना वः युष्मान् । एवं परस्परम् अन्योन्यं भावयन्तः श्रेयः परं मोक्षलक्षणं ज्ञानप्राप्तिक्रमेण अवाप्स्यथ । स्वर्गं वा परं श्रेयः अवाप्स्यथ ॥ ११ ॥
In plain words
How so? —
Nourish the gods — Indra and the rest — by this sacrifice; keep them thriving, make them grow. And let those gods nourish you in return, filling you out with rain and everything that follows from it. "You" here is simply you, all of you. Sustaining each other in this way, each feeding the other, you will reach the highest good, the good whose defining mark is mokṣa — reached by the graded sequence through which jñāna arrives. Or, on another reading: what you will reach is heaven, and heaven is the highest good meant here.
Close to the Sanskrit
How? —
The gods, Indra and the rest — nourish them, make them grow, by this sacrifice. Let those gods nourish you, let them fill you out with rain and the rest — vaḥ, that is, you. Thus nourishing one another, each the other, you will obtain the highest good, that whose mark is liberation, by the graded sequence of the attainment of knowledge. Or else: you will obtain heaven, the highest good.