What did Jesus mean by “buy from me gold refined by fire” and “salve to anoint your eyes” in Revelation 3:18?

When addressing the lukewarm Church of Laodicea, Christ suggested the following: Revelation 3:14-22 (ESV): 14 “And to the angel of the church in Laodicea write: ‘The words of the Amen, the faithful and true witness, the beginning of God's...