I would be absolutely lost without my 6 1/2" X 24" for strip cutting, my 9 1/2" square and my 12 1/2" square for any and everything else. Main thing to remember is to make sure all of your rulers are the same brand name. They do not all measure the same!
My brother owned and operated a quilt and framing business. He had a 16 foot Gammill long arm in his shop that he made me learn to use. His specialty was making tee shirt quilts and framing needlework. He also made me learn a computer. I like to think he was ahead of his time since he had a thriving on-line side of his business going for quilt kits. He died at age 55 in 2002. I just wish I had had room for his Gammill, but I didn't. However, I did rescue lots of fabric. I miss him so much.