Therefore they shall now be the first to go into exile,
and the revelry of the loungers shall pass away.
It was, in fact, the wealthy, ruling class who were taken into exile first as a matter of policy.
Verses 9-10 are odd. A note in the Harper Collins Study Bible summarizes them nicely:
A narrative sketches a mysterious and ominous little scene of survivors hiding among the ruins and the bodies of the slain.
In verse 12 Amos uses some proverbial statements to make the point out that the injustice found in Israel is not natural:
Do horses run on rocks?
Does one plow the sea with oxen?
But you have turned justice into poison
and the fruit of righteousness into wormwood...
Chapter 7 records the first three in a series of visions. When he sees YHWH preparing judgment first by locusts and then by fire, Amos intercedes and YHWH relents. The third vision is of a plumb line, or something. The Hebrew word is known only from this context. Whatever it is, Israel doesn't measure up and Amos doesn't intervene.
These prophecies are not, as one might imagine, welcome in Israel. This is perhaps especially the case since Amos was a hick from Judah. Verses 10-17 tell how the prophet was confronted by Amaziah, the priest of Bethel. This showdown is reminiscent of the confrontations we read of between Jeremiah and the professional prophets of Judah. In essence Amaziah says "Go home! Don't prophesy here." Amos responds that he is not a professional prophet. He gets the last word in with a nasty bit of judgment against Amaziah and his kin:
Therefore thus says the Lord:
'Your wife shall become a prostitute in the city,
and your sons and your daughters shall fall by the sword,
and your land shall be parceled out by line;
you yourself shall die in an unclean land,
and Israel shall surely go into exile away from its land.'
The visions resume in chapter 8. Here Amos sees a "summer basket" or "basket of summer fruit." According to the Jewish Study Bible there is a pun in the Hebrew. That basket, kayitz, signifies the end, ketz. The NIV tries to retain the pun making the vision a basket of "ripe fruit" and declaring that the "time is ripe" for Israel's judgment. Nicely done, NIV.
The remainder of the chapter is taken up with graphic details of the pending judgment.
Chapter 9 begins with the last of Amos' visions. This time YHWH is standing beside "the altar." Whether this is the alter at Bethel is not specified. YHWH declares to the Israelites that they cannot hide from his judgment.
All the sinners among my people
will die by the sword,
all those who say,
'Disaster will not overtake or meet us. '
Verses 11-15 are a promise that, at some future day, Israel will be restored and everything will be hunky-dory, if not better. The Harper Collins Study Bible suggests, plausibly, that these verses, which assume that Israel has been destroyed and its people exiled, probably were written by a later hand.
Biblical quotations are from the New International Version. The image of Juan de Berogna's painting of Amos came from this website.