You won't be buying anything as that's illegal when running a private server.
Donation: A donation is a gift given by physical or legal persons, typically for charitable purposes and/or to benefit a cause. A donation may take various forms, including cash, services, new or used goods including clothing, toys, food, vehicles, it also may consist of emergency, relief or humanitarian aid items, development aid support, and can also relate to medical care needs as i.e. blood or organs for transplant. Charitable gifts of goods or services are also called gifts in kind.
What that means is by donating to us we will return to you a gift. You won't be purchasing p hats but instead will be receiving them as gifts for donating.