Hi all. I've never done this before and was wondering how much fondant it would take to do 2 dozen like this, and also, how big the circle would been to be (approx) for a standard size cupcake. Thanks!

I'm not sure how much fondant you will need but I don't think a lot though, it also depends on how thick you cut your toppers
Whereas to the size I use the 2 1/2" round cutter for the standard size
HTH

The size of the round depends on how much frosting or ganache you put under it. I Use the 3 1/16" (78mm) cutter for mine, but I use quite a bit of frosting under to get a nice dome - my cupcakes bake flat.

See this tutorial from Cake Journal for more tips: http://www.cakejournal.com/archives/cupcake-decorating-part-3

Thanks! Just what I was looking for!