It is always best when examining scripture to use the entire account in context, so if I may, here it is and I will give you my analysis and opinion.
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The Rich Ruler - Luke 17: 18-29
18A certain ruler asked him, "Good teacher, what must I do to inherit eternal life?"
19"Why do you call me good?" Jesus answered. "No one is good—except God alone. 20You know the commandments: 'Do not commit adultery, do not murder, do not steal, do not give false testimony, honor your father and mother."
21"All these I have kept since I was a boy," he said.
22When Jesus heard this, he said to him, "You still lack one thing. Sell everything you have and give to the poor, and you will have treasure in heaven. Then come, follow me."
23When he heard this, he became very sad, because he was a man of great wealth. 24Jesus looked at him and said, "How hard it is for the rich to enter the kingdom of God! 25Indeed, 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."
26Those who heard this asked, "Who then can be saved?"
27Jesus replied, "What is impossible with men is possible with God."
28Peter said to him, "We have left all we had to follow you!"
29"I tell you the truth," Jesus said to them, "no one who has left home or wife or brothers or parents or children for the sake of the kingdom of God 30will fail to receive many times as much in this age and, in the age to come, eternal life."
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A very interesting story. Christ, being God, obviously knew this rich man's heart. I always thought the man approached Jesus in a very public way with the intent of puffing himself up before Christ. First, the rich ruler attempted flattery of Jesus, but calling him "good" and "rabbi (teacher)." Since the account clearly states the man was of authority, as well as being rich, I imagine he tried this public confrontation in order to establish his piety in front of his subjects, and thus increase his standing. Christ quickly waved these ham fisted attempts off by asking him a question, and then going right to the heart of what he believed was a ticket to heaven - adherence to the Law of God.
Next, the rich ruler claimed that he adhered to the entire law 100%, since his youth to the present day. Basically, he was claiming he was sinless, which from scripture we know is false (Romans 3:23). The man was blatantly lying to Jesus (yet another sin).
Christ must have known that the man's greatest obstacle to salvation was his idolatry. His perceived power as a ruler was idolatry. His wealth was idolatry. So was his pride.
Idolatry is one of the sins that keeps us from God - and God hates it. It is in conflict with the Spirit of God.
16 But I say, walk by the Spirit, and you will not carry out the desire of the flesh. 17 For the flesh sets its desire against the Spirit, and the Spirit against the flesh; for these are in opposition to one another, so that you may not do the things that you please. 18 But if you are led by the Spirit, you are not under the Law. 19 Now the deeds of the flesh are evident, which are: immorality, impurity, sensuality, 20 idolatry, sorcery, enmities, strife, jealousy, outbursts of anger, disputes, dissensions, factions, 21 envying, drunkenness, carousing, and things like these, of which I forewarn you, just as I have forewarned you, that those who practice such things will not inherit the kingdom of God.
Galatians 5: 16-21
So, the man broke the law. The wages of sin are death. Case closed - except, Christ came to save. That was His mission. He was ministering directly to this rich ruler who not only tried to trip up Christ in public, but also wanted to exalt himself.
Jesus has a way of getting right to the heart of the matter. In this case - Christ went right to the man's idolatry in wealth (and the power that went with it) and confronted him with it to repent and change.
Christ emphasized this further in Matthew 6: 24 during the Sermon on the Mount:
No one can serve two masters. Either he will hate the one and love the other, or he will be devoted to the one and despise the other. You cannot serve both God and Money.
This is probably the actual site He gave that sermon. I find this amazing that we can see it even today:
The man, however, rejected that offer, and rejected Christ.
It is by accepting Christ that we are saved. Not works of our own doing. Nothing can save us, except accepting by faith Christ.
"For by grace you have been saved through faith, and that not of yourselves; it is the gift of God."
Ephesians 2:8
Jesus had not yet been crucified, but He was already gathering those sheep who would listen to His voice to Himself.
Even after the man rejected Him, Christ taught His disciples that grace was available to save.
Fascinating, isn't it?
Unfortunately, that Biblical account has been twisted and falsely used by some to justify terrible doctrine and even tyranny in the world, by claiming that Christ was Himself a Marxist since He told the man to sell his wealth. Of course that is rubbish, for Marxism and Communism themselves are spiritual problems in that they are idolatry also. Marxism is the idolatry of the State, of sinful Man, over God and His Word.
Christ knows that we need "things." He said so.
31So do not worry, saying, 'What shall we eat?' or 'What shall we drink?' or 'What shall we wear?' 32For the pagans run after all these things, and your heavenly Father knows that you need them. 33But seek first his kingdom and his righteousness, and all these things will be given to you as well.
Matthew 6: 31-33
Christ has to be accepted to be saved. God has to be first. Sin can be forgiven, but Jesus has this divine way of exposing to each of us what our spiritual problem is.
Do you lack that one thing?
I am not sure what you mean exactly. I lack many things sometimes. I am a sinful man. That is why I need Christ to save me.
Following Jesus is good advice. He gave the same advice to the rich ruler.
What is your interpretation of Luke 17: 18-29?