Triangles have always been my preferred doodle typology. They're in the margins of my tenth grade trig homework and all over my airplane napkins. There's a rhythm to triangles. Their constraints and their flexibility produce an irregular pattern that can go on and on, crashing into or skirting along the edge of my paper.
Draw two adjacent triangles on a piece of paper, and their relationship tells you where to draw the next one, and the one after that, and the one after that.