I used a "cutoff" for my jib sheet. It came at a good price. It's ludicrously oversized, I could lift boat, trailer and towing vehicle with it, but it feels good and had the right length out of the box. Will be a while before I replace that, even though it's really too heavy for light airs.
Using the same rope everywhere makes it really hard to tell things apart. I made the mistake of buying a single color for my spinnaker sheet. Had to throw one half of it out and replace by a different color, it was just too annoying not being able to tell which was which. (Now, I run my sheets loose in the cockpit, it might be different if they each emerged from a fairlead on opposite sides of the cockpit, like jib sheets, but the way I have them, the tails can get mixed up).
Also, for spinnaker sheets I found that the "official" table of recommended lengths definitely was off. I bought a bit extra and still it was barely enough.
If you have to economize, make sure to get the most low-stretch that you can afford for your halyards - it does make a difference sailing in gusts. A stretchy halyard will allow the sail to have more belly in a gust, precisely the opposite of what you want to have a positive sailing experience. For sheet's, you are manually adjusting anyway, so it's not that critical.
As Tom noted the thread "
Ropes for various lines" contains a rather detailed discussion.