A little more about natural law, the rules and punishment within natural law? There are some things about the natural law (in Christian perspective), which I do not understand. If I have understood it right, then the natural law is based on our conscience, like everyone know that killing is wrong.

If natural law is based on conscience we received from God, should not we all act alike? That it's just based on luck? Like if you have a wealthy family that gives you everything you want, then you're just stupid if you steal, but if you on the other hand steal to support you're family, then you perhaps feel like it's you'r only hope?
Charles Rice addresses this question more or less in his 50 questions on the Natural Law.  (See q. 35).  

I'll try and synthesize it a bit while my new baby forms his or her conscience about whether or not today is a good day to be born. He mentions three reasons why your conscience is subjectively culpable (and, being subjective, not the same as anyone else's by degrees). 


Not all consciences are formed according to the "moral obligation to see the truth". 
A conscience should always be followed regardless if it came up with the right conclusion. 
A doubtful conscience should never be acted upon, but sometimes is. 


So, in all those cases you see people acting in ways that are the opposite of how we objectively should act. Ignorance, pride and cowardice can increase the odds of people acting that way. And, to your question, the love of money increases our vulnerability ignorance, pride and cowardice.  

Still, stealing is unjust in any circumstance  and violates the 6th commandment in a pretty obvious way. If a person is incapable of acquiring sustenance then they're actively being oppressed any civilization that does that is doomed (mainly according to the Natural Law principle of solidarity).

Pope John Paul II wrote "it is not wrong to want to live better, what is wrong is a style of life which is presumed to be better when it is directed toward 'having' rather than 'being'".  So we'll never be royalty, oh well.  As my favorite priest said, the best way for a man to make sure he is poor and happy and not greedy is to have a big family, and that is a good that is far more in accord with the natural law than what the average rich man seeks.