what should I make out of clay ?

You should make a cat out of clay maybe a cat charm unless you dont like cats maybe another animal.

What kind of "clay" do you have though? --polymer clay, one of the air-dry clays, epoxy clay? (I'm presuming you don't have plasticine-type "modeling clay" since it sounds like your clay was able to be hardened.)

For polymer clay, check out zillions of possibilities at my polymer clay encyclopedia site (easiest to do by scrolling all the way down its Table of Contents page):

http://glassattic.com/polymer/contents.htm

And if you're only making "sculpted" items with your clay, any of the sculpted polymer clay items discussed there would often work for other clays (but some not with the detail, strength, waterproofness, etc, that polymer clay will give).

Cups and plates. You won't have to spend that much money on cups and plates