The blue (regular) neon goby is what I would recommend. They are the hardiest. You also want to get tank raised neon gobies. If they are not tank raised, they are usually not very hardy, whatsoever.
A pair is sometimes good (as I keep a pair in my tank), but you NEED to get them paired. If they are not a male/female pair, they will often fight to the death. This would be counter-productive to the ich problem, because they would be more concerned with fighting themselves, rather than the ich problem. Since I do not know how SWF.com sells thier neon gobies, I would recommend just one.