I haven't bought but maybe two patterns in 2.5 years of quilting because I've made simple quilts, Mostly small ones. I like a little bit of math but if I look at a pattern that has a lot of different colors with a design that would slow me down from getting started, I figure I'm doing good by rewarding and supporting a fellow quilter for figuring out all the measurements and steps for me.
As as for rulers, I have used every one that I've bought except for the twister. But I will! It's just so darn cute , but is not on the top of the list yet.