I am planning to install a half bath in the basement. Plumbing provisions are already in place as there was once a bathroom in the location I am remodeling. I had a ground water issue but that has been solved as I had a french drain installed with a sump pump unit. in addition, drylock was painted on the walls by the previous owner so now the basement is nice and dry - at least as dry as a basement can be.

Now to my questions - I plan to finish 3/4 of the basement at some point; however I am focusing on the bathroom as it is much needed. I want to ensure that when I construct the bathroom the insulation is done properly so when I do finish the rest of the basement it's consistent. I plan to construct my walls with metal studs. When I drywall I also plan to leave a 3-4" gap before the floor in case I have a water problem (i.e. sump pump fail). how should I insulate? Adhere rigid foam to the wall? Do i need a vapor barrier? Do I have to insulate the ceiling? What is the best process for my scenario?

If it matters - the house was built in 1950; foundation is poured concrete; I have forced hot air and air conditioning with supply vents in the basement.