A sacrifice to God is a broken spirit.
Psalm 50:19
Do not regard the external, but concentrate your gaze on the internal, gather up the entire world into the noetic cell of the soul, prepare for the Lord a temple which does not contain any idols.
Venerable Nilus of Sinai
God smells not matter or sensory aroma, but the noetic and spiritual. The most pleasant incense is the soul of the one who offers it. Through spiritual sacrifices we recognize not only the stifling of passions but also the dedication of all our natural powers to God, bringing them as a whole burnt offering to God in the fire of grace.
Venerable Maximos the Confessor
If you wish to offer gifts to God, emulate the widow and from your soul bring two mites - humility and love.
Venerable Theognist