Yes, every Christian should read the Gnostic gospels, because they add insight and history into Christianity and the salvation story. A Christian should read all of the surrounding literature that they can, including the apocrypha. It adds context, and lets the Christian know what some of the criticism of Christianity are, and what critics were saying at the time.
The Holy Bible was compiled during the Dark Ages by the Catholic Church. Protestant churches still use this compilation even though they don't ascribe to Catholic ways. Every Christian should read the Gnostic Gospels simply because there are more stories to tell in the New Testament than just Matthew, Mark, Luke and John. Some of the Gnostic Gospels were written before the four main Gospels of the Bible. That means they may paint a more accurate picture of the life and work of Jesus Christ. The Gnostic Gospels include more than 50 ancient texts. Part of the controversy surrounding these texts is that many purport that the way to salvation is within each human being rather than through Jesus Christ. If more Christians knew that, the hierarchy of Catholic and Protestant churches would be destroyed and there would be no money and no power involved in these churches whatsoever.
I believe every Christian should take the time to read the Gnostic gospels. For many Christians, they don't even know what these gospels are because they were removed from the Bible by the Catholic Church so many years ago. I think these gospels are important for the true understanding of Christianity and how it came together.
The Gnostic Gospels where denounced as heresy for contradicting certain Christian doctrine and adding to it, for example the Gospel of Thomas talks about pantheism (God is everything) which is against Christian orthodoxy. These books were written after the 1st century (when the new testament was completed) and were centuries too late to be considered eyewitness accounts of Christ, as they contain mythological elements such as Jesus being a giant when he left the tomb.
I do not think every Christian should read the Gnostic gospels because not every Christian wants too. Some may not even know what that is and that is okay. We may all believe in the same religion but that does not mean we all have to act and show that belief the same way.
There is no right or wrong way to being a Christian, and no one person can say what a Christian should or should not do to worship. It is all in that individuals faith, and how they think that they should worship to practice their own faith they believe in.