Getting the big overview of a book in the Bible has been very helpful to me. What you mentioned, Carol, regarding who James was writing to, and knowing the background was immensely helpful to many of us when we went through his epistle last year! Many, who had somewhat written James off as being all Old Covenant, testified the same thing and got fresh light from James!
The same was true when we went through the book of Revelation. Previously it had been a very mysterious and frightening book to many of us. But after learning a few overview basics, it became the most wonderful book of God's love!
And I can say similar things about Hebrews, which we are just finishing up now. Before, many of us thought of it mainly as a book of warnings, with a few encouraging verses sprinkled here and there. But now, it too has taken on a whole new light - the entire book is a HUGE encouragement!!!
Someone a couple years ago said that anything discouraging is not of the Lord - He is the God of ALL encouragement! I now see that as we receive His light - like in the three books mentioned above - we come to see it is really the most encouraging! PRAISE HIM!!
However, that doesn't mean there is a not a downside for not running the race. As with any goal, there is the potential gain or potential loss.
Therefore, even if the 10 virgins or faithful/unfaithful servants parables in Matthew were not specifically written for gentile believers, there still is certainly some application - which I think is what we (Carol, OBW, me) are saying, right?