stainless wire would be a good start as for gases an Argon+CO2 mix at 75/25 although I dont use this mix Argon/CO2/Helium its supposed to be good if excessive heat is required (dont know, as I use the Argon+CO2 only, which is suffice for what I do) mine is a cebora 130turbo(snap-on) There will be people with more experience of stainless with a few good tips probably, I have only welded a couple of bike exhausts
Would be better off with lower CO2 content in the shielding gas. Too much CO2 causes the chromium in stainless to oxidise making the weld brittle.
The proper gas to use is 98% argon with a tiny bit of CO2 or oxygen to make the welds less pointy. Argoshield Light or similar (95% Argon and 4% CO2 with the rest oxygen) is fine for most people.
Stainless is horrid. Never as nice to weld as mild steel.