Your confusion about Mark 10:25 is understandable: "It is easier for a camel to go through the eye of a needle than for a rich man to enter the kingdom of God."
We are told that one of the many gates into the city of Jerusalem at the time of Jesus was so small it was known as "the eye of a needle." So Jesus was perhaps making a reference that his listeners would have immediately understood.
Of course, we know that Jesus had a rich sense of humor. I don't think it's unlikely that he was referring literally to an eye of a needle—deliberately creating an absurd image to make people laugh, and at the same time making an important point.
By the kingdom of God, Jesus is referring to that state of consciousness in which we are perfectly expressing our true spiritual energy and purpose. The rich are as fully the Christ in potential expression as the poor. But it's more difficult to move to a higher consciousness when we are burdened down with accumulations from the old consciousness we must leave behind. That's why so many of Jesus' followers were people for whom the old consciousness wasn't working; they had very little to lose by stepping forward in faith, and much to gain. Like the rich young man who wanted to follow Jesus but couldn't bring himself to part with his property, we find it harder to "let go and let God" when we've become laden with possessions and distractions.