If you don't wish to make your ginger syrup, good commercial ginger syrup is pretty widely available, and I included a link above to one from Amazon.com.
Ginger beer can be both alcoholic and non-alcoholic. We like an ale (alcoholic) ginger beer. Use your favorite.
Calories are an approximation only (from MyFitnessPal.com) and based on 2 ounces Crabbie's Ginger Beer and 1/4 teaspoon Fee Orange Bitters. I did not include garnishes as they vary.