2 Corinthians 8:9 is referring to the Glory and Honor and true riches that Jesus had before the world was. (John 17:5) He left that and took on the form of flesh.(Phillipians 2:7,8)
Him taking on flesh allowed us to become rich, He is that Tree of Life, that we may eat of and live forever.
James 2:5 relates with Revelation 2:9 very well. Historically they were very poor, but when everything is taken from you or discarded, your trust and faith increases tremendously because you are relying on the Lord, many times for your next meal, as well as protection. It is prophetic as well because during tribulation or the time of the antichrist, you may not have food, you will have to rely on him for that as well as shelter, protection, guidance... and everything.
I lived on the streets for a total of 9 years, getting rid of my bars of silver, gold, and possessions and gave myself to intensely searching the scriptures daily and sharing it with others. He massively increased my faith (Romans 10:17) and though I didn't have much, he was very faithful in always providing for me. I could lay down and sleep at night, outside without fear, believing in his promise of protection.(Psalm 4:8 * Isaiah 26:3)
He showed me the true riches and now I can walk through this world without fear as He has proved Himself to be true to His Word.
Psalm 91 gives me great hope for the future and during the things that will be coming upon this world.
2 Corinthians 6:10 As sorrowful, yet alway rejoicing; as poor, yet making many rich; as having nothing, and yet possessing all things.
Proverbs 13:7 There is that maketh himself rich, yet hath nothing: there is that maketh himself poor, yet hath great riches. (Finding those in need to give to will increase the riches inside of you, as well as increase the faith in others)
The motive has to be love, otherwise it is wood, hay, or stubble.
Many of the poor have become humbled and are able to hear God speaking to them plus they have less distractions. The scriptures say that He will arise to humble the whole earth.
Revelation 3:17 Because thou sayest, I am rich, and increased with goods, and have need of nothing; and knowest not that thou art wretched, and miserable, and poor, and blind, and naked: