For earrings you can go high or low..it really depends on your idea of quality and what is acceptable to you or the person wearing them. Our earrings are G, VS2 and I love the fact that they are higher quality than most earrings (plus my ring is a G VS1 so its a match!) and they have a great cut for earrings. As the others noticed, earrings are usually around H/I SI2/I1 for the general buying public. If it were me buying again or upgrading, I would go G/H and SI1/SI2 as the LOWEST. I'd really prefer VS2 just because now I am spoiled!
But try to get a good earring 'cut'. Sometimes earring stones are not the best cuts because people don't really think to check that..its just an earring. But the cut can make a huge difference. My earrings now vs my old ones with too large table and too large depth look very different, and much better. Stay away from large table, large depth combos (e.g. table 63%, depth 65%) as you will lose alot of light out the bottom, and also the stone will look smaller than it is due to some of the carat weight being carried in the depth of the stone.
If you are looking online, places do carry the H/I SI2/I1 quality but many times they also carry a G/H VS quality as well. So you should be able to find what you are looking for, regardless of color/clarity. Ask some Q's about the cut. If you are on a tight budget, H/I SI2 would be your best bet IMO.
Just don't go to Macys or the like! They don't grade their diamonds, so half the time you end up with a J colored stone and I1-I2 clarity!! John Q Public doesn't know any better.
Good luck!!