I am making a wedding cake this weekend. It will be 4 tiers, square, covered with fondant. At the base of each tier will be a green ribbon about 2 inches wide, with a large 2 loop bow on the 2nd tier from the top with the ribbon tails streaming down the bottom 2 tiers. Should I make the ribbon and bow out of fondant or gumpaste?

You can mix half fondant and half gum paste.

I'd go with 50/50 as well.