The basic materials for nature journaling are simple: a notebook and a writing or drawing utensil:
There are so many options for purchasing journals from very inexpensive notebooks to elaborately designed field books, and your choice will mostly depend on your preferences as to where and how you will be doing your nature journaling. Some students prefer journals with blank pages, others like the dotted and lined pages. Some students like to collect flowers and leaves, so a field folder would be appropriate. The important element is to have a place to keep your journal responses all together as a record of your thinking and for reflection purposes.
Many of my students use simple blue or black ink pens; however some like to use colored pencils and watercolor markers, especially if they are sketching. Try to avoid using pencil as that tends to fade over time. Again, the choice depends on your preferences and how you plan to use your journal.
Bring binoculars, especially if you are bird watching.
Cell phones or cameras for taking pictures, only! NO texting or chatting while you are journaling.
Bring a folding chair or stool for sitting.
Bring a small day pack bag to carry your materials as well as water and snacks.