Through devotional service one can easily please Lord Kṛṣṇa with a leaf of the tulasī plant and a little water. As the Lord says in the Bhagavad-gītā (9.26), a leaf, a flower, a fruit or some water (patraṁ puṣpaṁ phalaṁ toyam), when offered with devotion, very much pleases Him. He universally accepts the services of His devotees. Even the poorest of devotees in any part of the world can secure a small flower, fruit or leaf and a little water, and if these offerings, and especially tulasī leaves and Ganges water, are offered to Kṛṣṇa with devotion, He is very satisfied. It is said that Kṛṣṇa is so pleased by such devotional service that He offers Himself to His devotee in exchange for it.
jalasya culukena vā
vikrīṇīte svam ātmānaṁ
“Śrī Kṛṣṇa, who is very affectionate toward His devotees, sells Himself to a devotee who offers Him merely a tulasī leaf and a palmful of water.”
This is a verse from the Gautamīya-tantra.
Ref >> Srila Prabhupada Vani.