The Tempest..

Which act is that?

Sorry, Act 1

As far as act one goes, I'd say that Gonzalo is a foil to Antonio and Sebastian. Gonzalo is one of those good guys who isn't seeking to further his station in life. He is content to do his job and think the better of other people Antonio and Sebastian are conniving manipulators only interested in bettering their own fortunes at the expense of others. Ariel and Caliban are also foils to each other. While they are both servants, Ariel is considered Prospero's golden child or golden fairy I guess. Ariel is treated with respect and kindness while Caliban is treated like a slave. While Ariel is sort of working off a debt to Prospero, Caliban is thrust into servitude for attempting to rape Miranda.