Some rulers have a little bit of texture on the bottom side that helps the ruler to grip and hold the fabric securely as you cut. I prefer those, but it's a personal choice. There are all shapes and sizes, and you'll want them all eventually. Sharp needles that don't snag our beautiful fabrics. It's definitely time for a new needle.
Some machines have markings on the throat plate.
Others have special presser feet. It's important that the seam be accurate. Imagine more blocks, more errors. Now measure the center square carefully. It should be exactly 2 inches across.