Hello all--I have a bathroom rough in in my den level townhouse. Concrete floors, no walls...rough! I'm thinking about slowly transforming it into an operational bathroom as money becomes available, so it would have to be done piecemeal. So, as professionals, where should I start? Drywalling? Tiling the floor? Wiring? I'm a novice here. Thanks

figure out which drain pipe stub ups go to which fixtures.
lay out your walls accordingly.
locate any already installed future vent.
install your walls.
bring in your 1 piece tub or shower and set in place.
run your drains and vents.
run the water piping including shower valve
run the wiring.
install the bathroom vent fan and duct
call for rough inspections.
insulate
apply dry wall
tile and paint.
install fixtures
celebrate with some good food and the beverage of your choice...

1.You design it on paper.
2.You build the stud walls.
3.You rough in the wiring, plumbing, HVAC, etc.
4.Inspection.
5.Insulation.
6.Inspection.
7.Paint +trim work.
8.Floor covering.
9.Set plumbing fixtures, electrical devices.
10.Inspection.
11.Begin occupancy.

Packy + I were typing a response at the same time. We tend to think along the same lines.