I also have a limited selection of rulers - I have a 3"x18" (my first ruler), a 12.5" square and a 6.5" x 24". I do most of my cutting with the last two and can do pretty much anything I want with them (including the string quilt I posted on the last VQW thread). I also have a "Scrap Saver" mini ruler thing that helps with HSTs and QSTs but I have no recollection of where, when, or why I bought it. I found it in the bottom of my regular sewing box when I was looking for elastic for masks earlier in the pandemic. It has markings for alternate 1/8ths" but not 1/4s" so it's only really useful with certain-sized blocks.
I can certainly see the appeal of having the perfect ruler for everything, but at present my quilting budget is pretty limited so I'll save my pennies (and dollars) for fabric. :-)