My 5 year old daughter wanted to be Aurra Sing from Star Wars Clone Wars this year (my son was Cad Bane). Pretty simple except for the head piece. She already had a pair of red leggings. I went to the thrift store and bought a red tank top. We already had white makeup (I always buy makeup after season so it's cheap and we have it for next year if needed).
I also got lucky and found a hair piece at the thrift store. I think it is hair used for a weave. There was a string attached to it that held it together. I kept that on. I bought a bald cap from a Halloween store. I cut a tiny hole in the bald cap (it stretches) and pulled the string from the hair through it. I then taped the string to a piece of cardboard I cut out and glued that to the inside of the bald cap.
I took an old t shirt of my son's and cut it up and used that to make the large red pony tail band for the hair and also used it to make the arm band and wrist bands. I put the makeup all over her face, neck and arms and also the bald cap. I used gray makeup around her eyes. My husband made a holster out of some chalk board material I bought at Joann's (my son needed holsters, too).
I had a belt that came with some pants that I never wore. I wrapped that around her twice and attached the holster to it. I bought a costume gun that we were going to attach a pole to for the sniper rifle, but we ended up running out of time. She ended up carrying a clone rifle for pictures but didn't walk around with it. The only problem I had was that I didn't put the ponytail high enough on the bald cap so it ended up drooping a little.
Also I think rather than using the cream makeup I would use a white cake makeup. It would be harder to put on, but it wouldn't come off so easy I don't think. It didn't cover as smooth as I would have liked. I think it turned out great, though. In total, this Homemade Aurra Sing Costume cost me $10.