Can I pay for Netflix with my apple giftcard?

Please make sure that what you are actually asking about is an iTunes/App Store Gift Card, not an Apple Gift Card. They are two different things and are not interchangeable.

Apple Gift Cards can only be used to buy Apple products. You need to redeem an iTunes/App Store Gift Card to pay for subscriptions.

ASC - Late 2012 Mac mini, macOS 10.13.3;  Watch, 38 mm AL, watchOS 4.2.2; iPad Air 2 & iPhone 7+, iOS 11.2.5; TV 4th Gen, tvOS 10.2.5;  Airport Express

Yes. If your account has enough gift card balance, the balance will be used first to pay for any subscriptions.

If there is not enough, it will se the gift card for as much as it can, and will charge the rest to the associated credit card.