Stainless is not an easy way to get a start. It doesn't tolerate overheating all that well, is hard to get up to temp and once you get it up to temp it's really easy to overheat it. You might want to consider going with 4130 and bronze brazing alloys as a cheaper alternative. However, you would definitely need an oxy/fuel torch for that.

If you were going to stick to silver and stainless:
You want 76975A64 filler

You probably want black flux 7645A41

I can't recommend starting with plumbing torches, but some people report success with MAPP and silver