I had just a 6x24 & 6x6 for AGES. Then I got a 15x15-ESSENTIAL for squaring up blocks. Then 6x12, handy and easier to handle. I got a 4x14 in a kit I won from Babylock, also extremely handy. I bought a set of 4 square rulers: 4.5, 6.5, 9.6, & 12.5 for $18 when 1/2 off at JoAnns. I also have a tiny one or two somewhere that came in kits. But I'd really like a 8x24 for easier cutting of 6.5" strips. I guess if I could have just two, I guess it would be the 15x15 and the 8x24. But I'm sure glad I don't have to restrict myself.