For stainless MIG you need Argon with a little CO2, perhaps 3%. The wire grade is dependent on what the manifold is made of; there is a chart here in the MIG how-to guide.
I use this wire for 304 and 316 - handy if you don't want to invest in a large reel. There are other threads on here somewhere about the choice of gas but the conclusion was that for hobby use Argoshield Light is a good compromise.