I used some of those 'butterfly' clamps, too...left over from my granddaughter when she was a baby. They didn't hold too well in Brody's super silky hair, though...they seemed way too heavy for the amount of hair and had no grip. Also, I found some latexy-rubbery-coated metal 'snap' clips that were really tiny...the kind that have a little curve in them and you press on them to 'bend' them and they snap-click-spring open...one way to open them and the other way to close them. They were less intrusive for Brody 'cuz they were very lightweight, and the rubbery coating held the hair with a decent grip as long as there was not a lot of hair. I never leave metal ones in their hair unless I'm with them, though...too scary for me.
After the hair gets long enough, you can use a band or scrunchy. Check baby sections and dollar stores.