What type of champagne is good to use for Mimosa?

All about taste. Since the champagne is being mixed with a fruit juice, you most likely don't want to splurge and pay $200 on a bottle of Dom, but if that's what you want to do, go for it! A simple dry brut is my choice, but any of the other sparkling wines do perfectly well, too. Maybe try a rose or a spumante for a little bit sweeter of a drink. No matter what you choose, remember that just because a champagne is expensive doesn't mean it is necessarily good, let the drink reflect your tastes! Enjoy!