Who are Swift's satirical targets?
First, recall that satire uses inversion, that is, what is normally expected is turned upside down. Additionally, satire pretends approval, but the approval is intended to rebuke or debunk.
The satire starts right off with Gulliver. The first inversion is of the value of education. The most snobbish elite of the "real" London have similar pedigrees. Like them, Gulliver has a fine education. He is sent to boarding school and apprenticed to be a surgeon. But his patients have a nasty habit of dying. He purports to spend hours studying the ancients but the knowledge in theory fails him, and his unfortunate charges, in practice.
The Lilliputians are an example of the egos of the English colonizars gone awry. Their dimunitive size does not in any way lessen their appetite for conquest. They fail to recognize the worth or rights of others in the world.
A third target in the Lilliputian section are the struggles between Catholicism and Protestantism. The ridiculous squabbles between the warring factions reflect the petty fighting between the two religions: what difference does it really make which end of the egg is broken? Additionally, the power of the king is lampooned. In this telling, the king has god-like powers that should make the reader think of the Pope. No man, in Swift's opinion, shinning clearly through his satire, is that humans should possess such authority.