As a beginner quilter, I couldn't resist the allure of Bargello, so I dove right in. As long as you follow the directions carefully, there's no reason a beginner can't make a rather complicated Bargello.
That said, here's my best advice:
1. Cut a small piece from each fabric you're using. Number each fabric in the order it appears in your "color way," and make a paper chart of those fabric pieces and their numbers. You'll need to refer to this as you follow any Bargello pattern (even one you create yourself).
2. Choosing a color that will blend (like gray), buy a whole lot of thread!
3. Understand that what you'll be doing is cutting up a bunch of fabrics (sometimes as many as 21), sewing them back together in a different way, and then arranging them in yet another way. While the technique looks mystical on paper, it all becomes clear once you get into it.
4. Follow the directions and enjoy the result! When others are awed by your resulting quilt, don't tell them how easy it was. Let them think you are a wizard! (It'll make the rest of us look good, too!)