It depends on which path you want to take. You really don't have to buy anything that you wouldn't ordinarily have around the house if you don't want to.
You can use a notebook or loose paper and a pen or pencil. You can use an online Bible.
The important thing is that you begin your journaling journey and spend time with God.
If you want to go a littler further, there are other materials you may wish to get.
As mentioned in the previous post, if you plan to write or draw in your journaling Bible, you want to make sure you get the right kinds of pens and highlighters so that you will not have bleedthrough onto other pages.
Pigma Micron pens and Zebra Eco Zelite Highlighters have been highly recommended by journalers. They are available from Amazon.com, Christian bookstores and some craft stores.
For art work, you will probably want colored pencils or crayons. Some journalers really like Craylola Twistables, but I couldn't make them work for me. Probably a hand-eye coordination thing.
But my favorite by far are Prismacolor softcore pencils. They are expensive, but I have just been happier with the results. Go with what makes you happy or what your budget will allow. You are creating something for God.
I've mentioned before I don't paint. I just don't have a good place for it and I make a big enough mess with what I do use. So I can't recommend which watercolors or acrylics work best. However, elsewhere on this site, I've posted links to tutorials and other websites where the techniques are discussed.
If you like to draw or doodle, you can take it from here.
If not, there are some helps for you.
Some journalers prefer to use stamps, and there are a lot of choices in Christian stamps online and in craft stores. You will also need to purchase a set of acrylic blocks to use as a base when applying stamps. These are also available online and in craft stores.
Or you could use rub-ons or colorful stickers found at Walmart, hobby shops, dollar stores and online.
Another option is to use digital stamps which can be found online. Very similar to clipart. Just print out and color and place in your Bible.
Several websites, including this one, have free margin strips for you to print out and use. Some have strips that you can color. These fit into the 1.5" margins of most journaling Bibles. They are an easy way to provide some color in your Bible, but your greatest joy will come from expressing your faith in your own way.
Another option is PaintShop Pro. 30-day free trial is here.
Both of these programs run about $70 for the full versions.
The full version of Photoshop is much more expensive, but, of course, will do a lot more. You can buy the program or subscribe to the software online at Adobe.com.
As you learn more about journaling you may wish to try new things. Be sure to check out other blogs, and if you are on Facebook, check out some of the many groups dedicated to journaling in its many forms.