In a literal sense, the New Testament is for the New Testament Church or for the people that it was written to. James writes to the 12 tribes that are scattered abroad and in Revelation John writes to the seven churches in Asia.
Therefore the various letters or epistles are written to specific people with a specific purpose in mind. It doesn't hurt to know who they are written to or what for as that gives us a background into which the words have been written.
I have been doing quite a comprehensive study of the background to the New Testament Church which has been very helpful in understanding scripture.
Do the words apply to us? Yes and no. In its original application, no it doesn't so it is important to understand the why of the words as it can be used to mean what it doesn't mean, which sad to say is quite common.
We are constantly told to keep things in context and I think that we can only really understand scripture when we do that. As we understand the context we are better able to draw out any meaning for ourselves.
As an example, when it comes to the subject of money the prosperity preachers haven't got a clue as they have chosen to interpret scripture to fit their theology whereas we should make our theology fit the scriptures.
I have discovered that the Lord's prayer is not give us this day our daily bread but give us this day our bread for tomorrow. As I chased this thought and checked up on the background, I discovered that the New Testament Church never thought beyond tomorrow. If they went to bed with enough food for the next day they were content.
So prosperity scripture wise is food for today and enough for tomorrow. If they had a surplus of anything they gave to others who may be in need. As a very good friend of mine described prosperity as having enough for your needs and some leftover for others. If God wants to bless a person with more than that he is free to do so but it is not something that we strive for or preach to ask for donations to fill my coffers.
I have been told that more than one prosperity preacher has a house that cost 10 million dollars. I can't for the life of me work out why ANYONE needs a house that costs 10 million dollars not when there are millions of people on this earth who would be grateful for $10.