A Prosecco is a great "party" sparkler. So is a Spanish Cava, although those are getting more and more pricy.
Non-Champagne-region French sparklers are also good buys, like a
Blanquette de Limoux. For $12-15 you can also find a Cremant d'Alsace, a Cremant de Loire or a Cremant de Bordeaux. There are also good sparklers from the Saumur region. All of them generally are less expensive than sparklers from Champagne.
I tend to avoid the mass-produced California sparklers but I love some of the Californa premiums, especially Schramsberg, but their least expensive sparkler is their Mirabelle at about $20.