Welcome, maidtrx!
Experimentation really is the key - but there are some guidelines
that may help you.
Remember that the makeup is not a "mask" but should emphasize
your natural expressions so that when you change expressions they
are easily seen at the back of the room...
My face has been evolving over 30 years, and will still evolve.
My wife took an oval and drew face designs on it (saving time and
makeup and makeup removal!)
Or, you might take an actual photograph of your face and put a
layer of clear plastic on it and draw designs on that overlay.
Try taking a look at "Strutter's Complete Guide To Clown Makeup"
or Bubba Sikes has a great video "You Look Marvelous, Darling"
(
http://www.bubbasikes.com)
Since your wig and costume is almost all purple, I would be concerned
about too much purple in your makeup - maybe your teal accents could
be brought out in your makeup - if you can find that color.
Good luck, and post pictures if you can!
Ashes