No legitimate service (such as PayPal or banks) asks for payment via gift cards: Gift cards are scammers' preferred method because they are anonymous and untraceable, and once you send the code, there is no way to recover the money.
PayPal never requires an upfront payment to receive money: When someone transfers money to you via PayPal, it goes directly into your account. PayPal will never ask you to pay $20 USD or buy cards to "release" a payment you have received.