I'd glue the foam to the wall, tape and caulk the seams, then stud over it. If you want more R, fill the stud cavities w/ cellulose batts or mineral wool. They are both better insulators than fiberglass, and can deal with moisture better. I believe the consensus is to NOT use a vapor barrier in a basement, as the moisture that WILL get out can not dry to either side, so it stays and molds/rots/etc. See buildingscience.com and/or greenbuildingadvisor.com. Google Joe Lstiburek (and hope I spelled his name right. If not, he is mentioned all over gbadvisor). BTW: Use all the foam you can afford if you are in a cold place; the ground down a couple of feet can get pretty chilly. 8' down is not too bad.