I am a little tired, so if I make a mistake let me know. I haven't checked where you got your scriptures from, I don't think you mentioned it. But, it seems to be from Matthew ch. 6. If you look at parallel passage of Luke there is an additional specificity included. Here is the passage:
Luke 12:28-33 28 If, now, God thus clothes the vegetation in the field that today exists and tomorrow is cast into an oven, how much rather will he clothe YOU, YOU with little faith! 29 So quit seeking what YOU might eat and what YOU might drink, and quit being in anxious suspense; 30 for all these are the things the nations of the world are eagerly pursuing, but YOUR Father knows YOU need these things. 31 Nevertheless, seek continually his kingdom, and these things will be added to YOU.
32 “Have no fear, little flock, because YOUR Father has approved of giving YOU the kingdom. 33 Sell the things belonging to YOU and give gifts of mercy. . . .
Denominational gulf
Unfortunately, Christians are not sharing the same belief system. The differences are huge. Personally, I have rejected all churches and now use a Sola Scripture approach of a Harmonious interpretation that includes the entire OT & NT, and I use many translations, interlinear on the net translations to get to the heart of difficult things. I am not a Trinitarian, and I am neither a JW or with the LDS church. I do not mind my conclusions overlapping any one of all the Christian denominations that exist.
Explaining
The promise
is that Christ will become king by inheritance from King David over Israel. This Israel is not fleshly Israel, but is the entire earth filled with righteous believers at the end of the 1000 years. At first, many unbelievers may be included. (keeping it short)
As such there is Christ the king and highpriest residing in the heavens, his subkings and under priests - number given, 144,000 literal or not, who shall rule with him and be priests with him.
Rev 5: 9 . . .because thou hast been slain, and hast redeemed to God, by thy blood, out of every tribe, and tongue, and people, and nation, 10 and made them to our God kings and priests; and they shall reign over the earth.
Little flock:
Naturally, kings have subjects. Thus there are as is also natural a much smaller number of kings than there are subjects. This is the little flock mentioned in Luke 12:32 that will be given this privilege you quoted. Of course, if God wants to do so for other Christians who shall be subjects in the kingdom is up to him, and I cannot say that he will not do so. God does help all righteous people.
Subjects in the kingdom
These are named Great Crowd, or other sheep. At first, many non Christians shall also be resurrected as long as they aren't among the wicked.
Kingdom
If you need information on the kingdom and how, where, when, ask me.
Me
Though I believe God will supply us with our needs, not our lustful desires, I still believe that I have the responsibility to act as smartly as possible so that if I live beyond my means now that I have grown old, I must try to adjust to a smaller footprint and not rely on God to provide me as before.