Why dot grid
Dots give you alignment without the visual weight of a full grid: columns, boxes and lettering stay straight, and drawings do not look like they were made on graph paper. Most bullet journals use a 5 mm dot spacing, which is also about the height of handwriting on college-ruled paper.
Printing your own pages for a disc-bound or ring planner? Choose A5 with an 8 mm margin, or Letter and fold. Turn on Border if you want a frame, and set Big dot every to 5 to mark every 2.5 cm.