Depends on what purposes exactly you will be using your wants for. But if you have no set purpose (such as for only casting a circle) then you could place clear crystal quartz into the wand. The clear quartz will act like an energy amplifier for any other kind of crystal you may put with the wand. But it will also act under any property. Clear quartz can take on any of the properties of any crystal. Think of it like a multipurpose crystal.
Vanity is right indeed .Which kind of crystal or gem you would chose will depend of the the purpuse of the wand .Also i tend to go with gut feeling whenever i am designing my magical tools or objects of power .Even if you need matches with the common use of the stone you make sure also it feels right to you and it does the job before attaching permamently the gems .
Then you will be sure that the gem will work perfectly combined with the wood and with your own intend and energy .