I've shot a lot of different ammo through mine and I agree with most of the others here. For my gun I would break down ammo like this:
1. Federal Bulk (works great, comparatively cheap, my go-to ammo for the 15-22)
2. Federal: Lightning or Champion (worked great, slightly more expensive than bulk.)
3. CCI: Minimags or Stingers (works great but more expensive than Federal)
Other Opinions...
Wolf Match - These worked well but are expensive so I don't typically shoot them.
Eley Sport - These worked well but are again fairly expensive.
Winchester Bulk - These worked well but are not as easy to find here, I prefer Federal.
Remington Target - These worked ok but had more failures to fire than other ammo.
Remington Golden Bullets - I avoid these like the plague, I suggest you do so as well. They ran really dirty, increased feed problems, poor reliability.
I know I've shot a few other types as well but can't remember what they were. Obviously they didn't perform well enough or cost to much for me to make note of them for future use.

Stick with Federal or CCI and you should be set!