To this day I still use many of the same supplies that I used in college and one of my faves is recycling cracker and cereal boxes when they are empty- if you don't have the time or the money to buy canvas upcycled cardboard makes a great surface to do quick and expressive compositions and can hold up under lots of layers of paint- just what I like!
I start by cutting up my box
and then cover it in a couple layers of paint- not being too perfect of course!
then a little expressive writing and ANOTHER layer of paint
this is when I do a quick sketch- I prefer this exercise to be fast and free- this is a time that I choose to be expressive without worrying too much about composition
then I add my color with paint and a little more free writing