I like to order from keepsakequilting because the representation of their colors is right on. Never been disappointed but they are not inexpensive.
The pattern will tell you how much fabric you need but it may be hard for a newbie to pick the colors that match. Do you mean you'll make an all-white quilt or the base is white? Or do you mean the backing will be white?
My favorite batting is Warm and Natural or Warm and White. It handles beautifully, is comfortable to use BUT it is low loft.
As for the backing, there are some nice fabrics available in a variety of colors and patterns that measure wide enough for backing (conveniently called backing fabric). Some people like to use sheets - I am not one of them.