As a student I need to keep the cost down, so at the moment I use black notebooks from Flying Tiger. They have nice paper and nice sizes, for a quarter of the price of a Moleskin sketchbook.
The one I bring everywhere I go: My visual journal. It is small enough to fit in my smallest everydaypurse, and there is room for my businesscards as well in a pocket. The downside of this journal is that it has thinner pages than the others, too thing for my needs, so I need to skip every other page. This I sometimes switch to a moleskin of the same size – when I spoil myself.
The one I bring to social events and general travelling: My travelbook, small square sketchbook. (As seen on the above picture)
The one I bring to conferences and when I know I will be sketchnoting live: The Big Square sketchbook I take with me when I know I am going to an event where I will sketchnote, double the size of the small travelbook.