Welding Stainless Steel & Aluminum Tubing

[nymack66]

I am on a venture to LEARN to weld Stainless&Aluminium tubing. I am thinking on building a Radar Arch for the V.
I don't know where to start in regards to buying to correct welder for this job.
Any ideas are always welcome, I need to purchase a Welder first and foremost can anyone recommend what is consider to be the basic,mid or top end welder for this job?
My local access is Sears, Harbour Freight and Northern Tools etc ...