They key to a good turkey burger is using ground turkey thigh. It has more fat than turkey breast and won’t dry out nearly as easily. It’s kind of strange buying turkey thighs because the package never says thighs, but you can see that the color of the meat is much darker than breast meat.
I like to buy organic ground turkey thighs from Costco because they have the best price. After you form the turkey burger patties make sure to keep them cold in the fridge until ready to cook.