Better buy one with 111 beads, it´s a solar power number. 108 you can use, but it was said 108 is a incompleate number, it ties into saturn, but save to use, if only used for atleast 40 day straight. You can use 216 for workings, it´s the compleate number of 108, just use the 108 x2.
For binding 108 can be used. You can buy one for white magic and one for black magic. The wodden ones you can get for 3 USD. Beads out off stones can amplify your workings.