“Make unto you friends of the mammon of iniquity, that when you shall fail, they may receive you into everlasting dwellings.”
The Gospel today is highly allegorical. By “allegorical” I mean that it needs to be interpreted in a symbolic or representative way. The rich man is not a man at all, rather he represents God Who has entrusted His people with a varied treasure of gifts.
“The steward is man [each and every individual man and woman], to whom God has confided the various goods of soul and body, of grace and nature: faith, intellect, memory, free will; and five senses, health, strength of body, beauty, skill, power over others, time and opportunity for good, temporal riches, and other gifts.” The phrase “mammon of iniquity” was the Jewish way of referring to “wealth.” There is no iniquity when we use God’s wealth according to His plan.
God made each one of us to make use of His riches for His greater glory. As the Catechism says: “God made us to show forth His goodness and to share with us His everlasting happiness in heaven.”
We show God’s goodness when we make use of His gifts in accordance with His Commandments—but when we use His gifts contrary to His Commandments we are “unjust stewards” and we are liable to forfeit that “everlasting happiness in heaven.”
In the Gospel, the rich man commends the steward for his prudence—using his goods to ingratiate himself with the rich man’s debtors—but not, of course, for the theft of his goods. God, on the other hand, is more generous with us. As long as we follow his Commandments, He allows us to use His goods in a way that will ingratiate ourselves with the people around us. In fact, He commands us to “love our neighbors as ourselves,” which often enough will require that we expend the gifts He has given us. Indeed, He makes this personal, saying that when we help those in need, we are helping Him:
I was hungry, and you gave me to eat; I was thirsty, and you gave me to drink; I was a stranger, and you took me in: Naked, and you covered me: sick, and you visited me: I was in prison, and you came to me.
Amen I say to you, as long as you did it to one of these My least brethren, you did it to Me. 
Notice that some of these works of mercy to our neighbors require little or no money—which brings us to the fact that we can also use God’s gifts to help our neighbor spiritually. The Church gives us a list of the various works of mercy we can perform, both physical (corporal) and spiritual:
To feed the hungry;
To give drink to the thirsty;
To clothe the naked;
To harbor the homeless;
To visit the sick;
To ransom the captive;
To bury the dead.
To instruct the ignorant;
To counsel the doubtful;
To admonish sinners;
To bear wrongs patiently;
To forgive offences willingly;
To comfort the afflicted;
To pray for the living and the dead.
Some are physical and some are spiritual, but all of these rely on using the “assets of the Master”—the gifts given to us by God.
No Catholic should ally himself with “the unjust steward”—essentially a thief, who stole his master’s property. Yet, we must emulate his prudence: “For the Spirit Himself gives testimony to our spirit, that we are the sons of God. And if sons, heirs also: heirs indeed of God, and joint heirs with Christ.” May it never be said that we failed to exercise our inheritance with prudence and generosity! May it never be said that we squandered God’s gifts on immorality, or failed to help those in genuine need.
“For whosoever are led by the Spirit of God, they are the sons [and the daughters] of God.”
 Gospel: Luke xvi: 1-9 http://www.drbo.org/cgi-bin/d?b=drl&bk=49&ch=16&l=1-#x
 Rev. Fr. Leonard Goffine, The Church's Year http://sspxasia.com/Documents/The_Church_Year/Pentecost_8th_Sunday.htm
 Baltimore Catechism Q3 https://www.catholicity.com/baltimore-catechism/lesson01.html
 Matthew xxv:35-36 , 40 http://www.drbo.org/cgi-bin/d?b=drl&bk=47&ch=25&l=35-#x
 Catholic Encyclopedia, s.v. “Corporal and Spiritual works of mercy,” http://www.newadvent.org/cathen/10198d.htm
 Epistle: Romans viii: 12-17 http://www.drbo.org/cgi-bin/d?b=drl&bk=52&ch=8&l=12-#x
 Ibid. verse 14 http://www.drbo.org/cgi-bin/d?b=drl&bk=52&ch=8&l=14-#x