Paper. You'll need a paper that will withstand water and that does not tear or pill or buckle: my ideal papers are the lightest weight watercolor paper (usually 90 lb.), the textweight paper Velin Arches, or the heavyweight, printmaking paper Stonehenge.
Inks & Gesso. The inks should be lightfast, pigmented, and water soluble: I use FW Acrylic Inks, Australians can use Matisse acrylic inks for the same result. If you are interested in using gesso also, I recommend the one from Daniel Smith, Inc, because it is a little rougher and your book pages won't stick together when it dries.
Brushes. All I can say about the brushes is that they should be large: use 1" -3" wide, cheap brushes. This isn't about detail work. This is about movement, flow, and release. If your inks don't have a dropper tip, I'd recommend you purchase at least one eyedropper, possibly from a drugstore or scientific supply store.
Additional materials. A large water container and some paper towels are all you really need. Cut up a kitchen sponge, get a handful of twigs, gather a few pencils, grab some water soluble crayons for more painting experiences. Use a vinyl tablecloth to cover your painting surface.
I most commonly paint on Stonehenge paper and cut it up to make a Circle Accordion book (instructions are in the Painted Paper book and in all of my bookmaking books). It helps me to have a mood or theme in mind before I start, but it isn't necessary. I've had students do some freewriting: write whatever comes into their heads, then circle some words they want to work with and start by painting the words very large. Another example is to think about types of water: ponds, lakes, streams, waterfalls, toilets, gutters, oceans, tears, etc., and to see which of those speaks to you. Gather colors to support your mood.
Start by drawing with the ink in the dropper tip. Use a dry brush to spread it around. Dip the brush in water and draw out some of the ink. Whatever you like. Make your movements large, like a dance, and try to make different marks in different places. For best results, don't try to make one overall pattern. Vary the speed, the shapes. Try out sticks, crayons. Scribble with pencils. Just paint or throw paint. Ultimately, you will cut it up and it will change dramatically so you can't and shouldn't evaluate it yet.
Use a hair dryer periodically, or place the painting out in the sun clipped to a large board to dry. You'll be able to paint on top of it once it is dry and you can create multiple layers, letting the paper dry in between. The pearlescent colors are great for accents near the end because their particular ink sits up on the surface. Use a toothbrush to spatter the ink, or a serrated tracing wheel to make shimmery dotted lines. Add stenciled images with a dry, flat-bottomed stencil brush, if you like.
Cut the paper into strips, following the instructions for the Circle Accordion or the Drum Leaf Binding previously posted. Add content by flipping through the pages and see what they tell you or what they remind you of. Or, try to remember what you were thinking about when you began painting. What are you thinking now? What has changed? You might use that change for your content.