Use black pipe. Run the line downhill (from source) with pipe saddle hangers found at any decent plumbing supply. There is a ceiling bracket, all thread drop, & saddle fitting. It's cheap, easy, & flexable. Put plenty of t's on the lines, so as to allow later line additions. Use a t's instead of coupler fittings, with a plug in extra hole. Using t's is cheap insurance over the cost of a coupler, & the risk of having to tear apart later to add a run. Put condensate filter at end of runs, prior to coupler outlets, at a height that's reasonable to get to. This is the industry standard for shop air lines. It's cheap, & it works.
Galvanized pipe is only galvanized on the outside, which simply doesn't help anything. Copper works, but is very expensive these days. Black pipe will last a life time, which is probably long enough for most of us.

Joe