The only required material is paper or a journal!

Suggested materials from there (No need to buy anything if you don't have it - the whole point is getting creative with what you've got!) :

Glue or tape (ok so this one's required if you have other paper materials to use)
scissors
pencils, pens, markers
stamps
washi tape, stickers
scrapbook paper, paper doilies
magazines, newspapers
paper bags, gift wrap, tissue paper
post cards, photos

You can mix up elements of collage, drawing, stamping, and whatever else you want to try!