Some of the newer gins are considered terroir gins and are designed to give the essence of the surrounding lands. My current favorite is St. George. They offer three styles, all of which, while unique, showcase the local aromatics of the California countryside.
Try not to adulterate your lovely, high quality gin with a cheap grocery store tonic. The tonic you use may even be more important than the gin in a quality gin and tonic. Create a gin and tonic using high quality ingredients and you will never go back. It is like a different kind of cocktail all together. Artisanal tonic concentrates are are available at high quality liquor stores and are wonderful. You keep them in the refrigerator and dilute them with club soda when you are ready to use them. Many high-end bars however are making their own house tonic. I'll be honest, I haven't attempted it myself yet, but Im going to try it soon and I plan to use this recipe. Let me know if you get a chance to try it. Cheers!