Agreed, if you want to be able to rip it down quickly I'd go with the panda-film.. Possibly add some 2x2 rails for extra support if it will be sizable.. You'll want velcro stripping the length of 3 sides of your intended door, the rest can be tacked down.. You'll also want a way to reenforce the end of the cuts for your door as plastic cuts often like to travel..
If you'd rather have an actual wall then I'd check out hardware places to see what kind of lightweight paneling they carry.. Drywall is heavy, messy, and it takes a real pro to tape/sand it so that it looks really good when finished.. If you intend to pass this wall off as natural in a home done with drywall though, then this is the only way..
I once resorted to building a veg closet out of pegboard and panda film because there was nothing but drywall available.. That was actually a kickass method!
As for framing, there are options again.. You 'could' go with 2x2's if there won't be any switch-boxes in it, but stud length 2x4's are the norm, and often cheaper ($2 a piece here).. Stud spacing should be 24" (1 stud + 1 gap).. This is so 4' sheets meet up with the studs for nailing purposes..
Even cuts, and square corners are the key to a good wall.. You'll want a good level, and a good square if you don't want a ghetto wall..
You can build the frame box on the floor if you are positive you have the clearance you need to place it, and you are 'positive' the room height will match your wall height along its entire length.. Not very often a good idea in a renovation really..
Start with the ceiling plate.. Tack it up, then make sure your end studs are cut 'evenly' to proper length, and use them in conjunction with your level to place the floor plate.. If this will be in your basement, you will need a drill capable of drilling into some likely DAMN hard concrete, and special bolts called tap-cons to fasten the floor plate.. If your wall is less than 8' though, and you can fasten both ends really well to existing structure you can leave the floor plate floating on a divider wall..