What was the economy of the middle colonies?

The middle colonies were Pennsylvania, New Jersey, New York, and Delaware. The economy of the region was largely led by developments in Pennsylvania and New York.
William Penn (1644–1718) was the Quaker who founded Pennsylvania. He advocated religious freedom and political toleration. Thousands of able people emigrated there to enjoy those freedoms. Pennsylvania's economy prospered more quickly than that of any other colony. It had successful agricultural, fishery, tannery, and glass work industries.
Delaware became part of Pennsylvania in 1681. Prior to that, it had been ruled by the Swedes and the Dutch.
The history of New York starts with New Netherland. Founded in 1630, New Netherland developed a successful fur trade. The colony did not prosper, however, and the British took it over in 1664. The British established a more stable government that enabled the Dutch families to thrive economically. The fur trade continued, but grain became a major export. Powerful landlords controlled huge swathes of land, which were worked by tenants.
During the colonial era, New Jersey did not have a distinct identity. Eastern New Jersey looked to New York; western New Jersey was dominated by Pennsylvania.
In summary, the best way to understand the economy of the middle colonies is by a careful study of Pennsylvania and New York.