We're not experts but we know what we like. Here are a few of the supplies we use when we do Art Journaling.
The Journal: You can start with a sketchbook, a notebook, watercolor papers bound together, or older books re-purposed for art journaling. Our current journals are magazine style books: my daughters is an old Waldorf magazine and mine is a vintage barbershop quartet song book that we repurposed for our journals. Eventually I would like a bound book filled with watercolor and textured papers...a current dream...so in the meantime we're altering books and having fun doing it.
Gesso: By adding gesso to the pages of our book we can create a working surface without the worry of paint and product seeping through the page because it acts as a primer. We simply coat the pages in gesso, let dry and we have a surface to play on. I have two gesso's, each from a different company. The Stevenson brand is the best one for page prep...it goes on like a dream. I would recommend it over the other - Bob Ross brand. I purchased the Bob Ross almost 3 years ago (haha that guys hair forever makes me laugh) and it's held up well. It works great for the watercolor crayons in place of water.
Acrylic Paint: For adding color, texture, design, brightness, depth, drama, shading, blending and all sorts of wonderfulness. Use the best quality you can afford and one with a gloss factor. To make basic craft paint last longer and blend better add a slow dry medium such as gloss gel medium or slow-dri blending medium, there are many other brands that make this type of product...just check your art supply store.
If I were to recommend one expensive paint...it would a good heavy bodied acrylic paint in Titanium white (Golden paints). You can easily add color with crayons and it acts as a great base for watercolor crayon work. Acrylics with gloss in them are much nicer to write on then their matte counterparts.
Watercolor Crayons: Oh so much better than pencils. The kidlet only uses the crayons and hasn't even touched the paint yet. She loves them! They really are something wonderful as you can color directly onto the page or use a wet brush touched right up to the crayon tip to apply strong color to the page. You can also apply with gesso for a lovely soft chalky color.
We have Staedtler's starter set of 12 and we purchased a few individual Neocolor II water soluble crayons from the art store. I gotta say I like the Neocolor a bit more as they seem just a tad smoother. There is no clean up with these - so that's also a huge plus! Search for some video's to see how they work are.
Glitter: Stickles, stickles and more stickles. Oh how we adore thee. I'm sure there are other good glitters out there but we are kinda giddy over stickles. Smear it on with your finger and be happy.
Paint Brushes: Most of us have some paint brushes laying around the house, so use them! If you do have to purchase some I like the Royal Soft Grip brand in a natural bristle. There are better brushes to be had...it's all preference and budget.
Pens and Pencils: Drawing over paint and watercolor is not an easy task. I've yet to find the pen that really pulls this off. Gel pens are okay and Sharpies are good if the surface is completely dry. Charcoal pencils are my current favorite and I use them almost exclusively.
Stamps, masking tape, toothpicks for scratching and adding texture, bubble wrap for print making, the skies the limit for what you can use and may want to use. It's really about just having fun and making pretty little messes.