I first tried a French 75 at Arnaud’s in New Orleans and found it tasty.
Here is the recipe:
1 ½ ounces gin
¾ ounce fresh lemon juice (about ¾ medium lemon)
¾ ounce simple syrup (try honey!)
2 to 3 ounces chilled Champagne (enough to top the glass)
Lemon peel, for garnish
FWIW, Tobin James makes an inexpensive champagne that is perfect for drinks like the French 75, Kir Royale, and such.