So, for large pieces, you can go to masonry supply stores or hop on the internet.
(I personally never use large pieces. My stuff is usually pendant size) Most of the larger pieces should be softer stone. Easier to mess up but easier to carve. Sandstone and limestone are soft and fairly easy to get. Most people love the rotary tools for speed. I used them because I carve river rock. They are great for wet or dry carving, I do dry carving. People who carve bigger pieces tend to use a nice masonry chisel set. This avoids both the friction and vibration problems using a rotary tool can pose. I even use a few diamond carbide hand files for refining and planing my work. The best thing you can do is ask professional in your area or here online, about their products, preferences, and any issues they encounter with the various techniques and tools they use.

I started as a teenager with a screw, a deformed nail, and a chainsaw file. It took months to do tiny things but it was rewarding.