My question back to you is: what do you have at present? Then I'd ask you to look at OnmiGrid and Creative Grids rulers and see which one works best for you with your vision. I like both. Creative Girds doesn't need the sandpaper dots.
Must haves:
[1] that is 24" long, preferably 6" wide. I have trouble with the ones that are 6 1/2" or 8 1/2" wide as it is too easy to turn the ruler around and cut the wrong size.
[2] a 12" x 6" or 8: ruler.
-- Both of these rules would definitely have lines marking 30 degrees, 45 degrees, and 60 degrees.
Since I try to only buy rulers when I have a discount coupon from a LQS or other fabric store, I'd suggest that you do likewise and buy as you need and as you have coupons. I have also been given rulers by friends who found they had duplicates or triplicates. One friend found some at an estate sale in great condition.
My other favorite ruler is the Bias Square-up Ruler from Martingale/That Patchwork Place. I have the 8" one and use it a lot.
ali