If you're paying for food that has a delivery charge then common tipping etiquette for small and large orders is 15% for normal service with A $3.00 minimum; 15%-20%+ for great service (or if you're feeling generous); below 10% for poor service.
However tip whatever you can as not everyone can afford to pay the recommended tip to the delivery driver and that's okay and the delivery driver will understand.
But the delivery driver delivering your food makes most of their income through tips so if possible try to tip them the most you can.
The delivery driver will be very appreciative and will likely give you great and even better service the more you order and have delivered through them.