I only make cards for occasions like birthdays, mother's day, father's day, etc.
I use scrap materials collected over time. I find those table top calendar's paper is quite nice to use (the hard type).
those mouth/leg painter's calendars have nice pictures on them to use too..
oh, and i use scrap art foams i've gotten since primary school (im in uni now). Black, red, yellow, blue, green.