You don't need anything to make a margarita besides tequila, a liquor with citrus and sweet, and fresh lemon juice. There is really no reason to even consider a mix.
My SIl used to work at LaCasa here in Motown when it was open and they would take a can of frozen lemonade thawed and a can of frozen limeade thawed and add tequila and triple sec. Simple and delicious. You can serve on the rocks or mix in a blender with ice for frozen. Hope this helps.