Greg Gilbert has written a small book that will help with the above difficulty. In What is the Gospel?, Gilbert addresses in about 120 pages both what the gospel is and what the gospel is not. The author writes in an intentionally basic style that anyone could easily understand.
This book is ideal for all Christians. We must be able to articulate what the gospel is. This is important for us as individuals and for our witness in the world.
I encourage you to purchase several copies and give them out to your friends. Tell them to read the book and then pass it on. The book would be good for unbelievers as well. Gilbert pulls no punches and does not try to make the gospel "palatable" to those who might be offended by the cross. He simply tells what the gospel is from the pages of the bible.
Give these to your church family for edification and to your lost friends for evangelization.