A decent ruler is worth the money.
I have upgraded some of mine over the years.
The first ones I bought were the Quilter's Rule ones with the ridges on the bottom and the thick lines. I would not buy them again - mainly because of the thick lines.
The next ones were the Ominigrid Rulers with the yellow lines. I like the ones that have the very thin 1/8 inch grids on them.
I bought a couple of Creative Grids ones (8-1/2 x 24-1/2, 6-1/2 x 6-1/2, 3-1/2 x 18-1/2)
For me, there are too many lines and I have to "think" too much when using them.
And my current favorites - the Olfa Frosted Rulers. The lines are thin, and they are easy for me to read.
I wish the company would come out with a few more sizes of them.
Probably the best way to "save" money is to avoid buying duplicates, and making sure that the ruler is one that you might actually use.
I feel strongly that if a certain tool, or book/pattern, is called for when attending a class, please have it! It makes things so much easier for all concerned - the instructor, the other students, and oneself!!!