What can I use to build temporary walls in an unfinished basement?
Why not build a drywall curtain. Base plate pinned to concrete floor with a few Tapcon type screws. Studs wedged between base plate and joists. If wider than 4 feet, add a vertical stud. Cover in drywall. NOTE THIS IS NOT CODE AND MUST BE TEMPORARY ONLY!

Create a two or three sided room (but be sure to leave access, like a hinged plywood panel with a padlock, for emergency access to utilities).

If you plan on using this for more than one or two events, consider building real drywall structures (you know, 16 inch centers, etc.). If you skip the taping and mudding, these go up in hours, not days, and will work until you are ready for the real finish project. You do need to be sure to leave adequate ventilation around utilities and easy access. A prehung door also can go up pretty fast.