The Versa Tool by HandiQuilter is a great starter ruler. It's got a few different edges. There is a video on it. I got a great deal on ebay, about 1/2 the price. I like it. I have since also bought a boomerang shaped ruler from Deloa's and like that, although I've only played with that a little. If you are using them on a domestic machine, I think you will have the best luck with smaller rulers. You will probably also want a ruler foot. The foot that came with my Juki is thin and slips under the ruler. The ruler foot is thicker and glides along the edge.
https://www.handiquilter.com/videos/handi-gadgets/5/
http://www.deloasquiltshop.com/shop/guides.html