By just using black and white with some subtle shading you can make cards out of doodles. I have been flicking through a great little book that I bought for my dad a short while while ago and got some pattern ideas for doodling and with a little practice I am starting to get the hang of it now. My hands can be a bit shaky at times so some lines get a bit of a wobble in them but it is great fun to do. I will get your book back to you soon dad!
Pens: Black Pitt pen, pencil, paper stub
Card: Black and white card
Book: Yoga for the brain A zentangle workout by Sandy Steen Bartholemew