According to the Bible, after His resurrection, Jesus walked this physical earth for 40 days teaching exclusively on the Kingdom of God.  In my mind, this points to the progression being that once salvation for all was accomplished, the Kingdom was (and still is) the next step.  Salvation is a free gift.  The Kingdom of God must be sought. In the New Testament Jesus uses words like "ask" "seek" "knock" when speaking of the Kingdom, which leads us to believe that some action is demanded on our part if we are to earn the right to know the "mysteries" of the Kingdom.

The mysteries of the Kingdom are given to students who have shown themselves worthy. How is this achieved?  Study, or "memorization" of the scriptures alone is not the way. We see evidence of this in the story of the rich young ruler, a man who had studied the scriptures since childhood. There was no law he did not know by heart and that he could not quote from rote memory.  Yet, when he asked Jesus what he must do to be saved, Jesus answered, "Sell all you have and give to the poor."  The young man was unwilling to do this, causing him to turn away from Jesus and from entering the Kingdom.

Because this young man was "married" to what he already knew, he was unable to empty himself to learn anything more or new from Jesus.  Sometimes learning must begin with "un"learning.  Just as a fish in an aquarium, the human mind will grow to fit the container in which it is placed.  The larger the container, the more the mind will keep expanding.  The Kingdom of God does not come by observation - the Kingdom of God is WITHIN you.  In order for the Kingdom to continue to grow within us, we must clear out some space.  If we are full of religion and what we "know" - the Kingdom cannot grow in us.