But earnestly desire the greater gifts, 1 Corinthians 12:31

To understand the phrase "But earnestly desire the greater gifts" from 1 Corinthians 12:31, we must understand what means to live according to the spirit (Romans 8:5).
God is the origin of the perfections we observe in the cosmos, to these perfections we call them spiritual gifts.
The gifts are lived because we grow. They are way, that is, we all have a ranking of rectitude, of mercy. 
They are progressive and are linked together, an example of a bond: Blessed are the pure in heart because they will see God, Matthew 5: 8, in this example a gift in this case integrity returns contemplative activity, the law of return acts upon our actions (You reap what your sow), the spiritual gifts return spiritual gifts as in this case. 
The spiritual gifts are progressive because we bear fruits: the fruits of the spirit, Galatians 5:22-23 (love, joy, peace, forbearans, kindness, goodness, faithfulness, gentleness, self control); and the works of the flesh: Galatians 519-21 (wrath, strife, seditions, envyngs, murders, drunkeness, orgies, adultery, fornication, witchcraft, hatred, litigations, jealousy).
Tomas Aqunas makes a distinction between the spiritual gifts of the will: mercy, rectitude, continuous improvement, constancy (fear of the lord); and the spiritual gifts of the understanding: good discernment, wisdom and spiritual gift of knowledge.
The search of wisdom and the progressive thinking lead us to the greater gifts: the eternal life, the perseverance, the fruits of the spirit, and the spiritual gifts of understanding.
http://www.quintoevangelio.com.ar/en/articles/item/104-can-we-do-profecy-and-when-a-profecy-is-good.html