I guess a little depends on the market, where you live. How much would a magician or ventriloquist charge in your area?
Then I would suggest that you charge less. Not because I want you to undercut them, but that you do not have the experience yet. As your act improves and you get positive feedback, then you can charge more.
If you were the client, how much would you want to pay for your act?
The last thing I would want if I were you, is for the client to think you ripped them off.