I'm fairly certain Foundation Crossfit on 11th and Pike takes cash.

Yes, you can. Here's how to make your own tonic at home (courtesy of Imbibe Magazine):

Ingredients:

4 cups water
3 cups pure cane sugar (or less, if that's your preference)
3 Tbsp. quinine (powdered cinchona bark; available in some herb stores or online)
6 Tbsp. powdered citric acid (found in the bulk section of most well-stocked grocery stores)
3 limes, zested and juiced
3 stalks lemongrass, roughly chopped

Just in case the link for quinine doesn't come through, here it is:

http://www.zooscape.com/cgi-bin/maitred/GreenCanyon/questp513833/jornada33423824/viewsubsub101246

Tools:

Medium saucepan
Spoon
Strainer
Cheesecloth or coffee filters
Funnel
Glass bottles with lids or screwtops

Directions:

STEP 1:   In a medium saucepan, bring the sugar and water to a boil until the sugar dissolves, then turn the heat down to low.

STEP 2:   Add the quinine, citric acid, lemongrass, lime zest and lime juice. Stir well and simmer for about 25 minutes, until the powders are dissolved and the syrup is thin and runny.

STEP 3:   Remove from heat and let cool. Strain out the large chunks through a colander, then filter through cheesecloth or coffee filters to refine. This step can take a while—and many filters—as the bark is a very fine powder, so be patient.

STEP 4: Funnel the syrup into sterilized glass bottles, cover tightly and store in the refrigerator for up to several weeks.

The drink that turned me onto gin was a classic by the name of Satan's Whiskers (curled) -- how can you not like a drink with that name? Besides having a brilliant name, it's also a delicious drink that highlights gins best qualities while at the same time masking some of the strong herbal flavors that sometimes turn off fans of vodka.

Satan's Whiskers (curled)

I should note, this is my personal variation on the recipe. You'll find slightly different versions elsewhere.

STEP 1: In a chilled martini glass, give a wash of Grand Marnier. Pour out the excess liqueur.

STEP 2: In a glass filled with ice, stir 2oz of Hendrick's gin, a splash of both sweet and dry vermouth, the juice of 1/2 a medium-sized orange and a few dashes of Fee's Orange Bitters.

STEP 3: Pour the mixture into the martini glass and garnish with a twist of orange.

In Seattle, you can find Fee's Orange Bitters at Delauranti in Pike Place Market (the south end of the market), or you can buy it online. Just Google "fee's bitters"

Margaritas are a great, safe way to start mixing herbs with your cocktails because -- quite frankly -- they are very forgiving about your proportions. Add (1) a healthy amount of tequila, (2) at least 1 fresh squeezed lime or 2 of they are small/dry, (3) a touch of simple syrup or agave syrup, (4) and any one of the following muddled* combinations:

Green apple and rosemary (just a sprig for scent, do not muddle)
Cucumber and cilantro
Watermelon and thai basil
Blackberry and mint

Or, if tequila isn't your thing and your feeling all "pacific northwest," I had a heavenly Alpine Martini at a Belltown establishment several years ago. If I'm not mistaken, this is the recipe:

Mix 1.5 ounces citron vodka and 1 scoop of Douglas Fir Sorbet (recipe follows) in a chilled martini glass with 1 small cedar frond as garnish.

For the Douglas Fir Sorbet:

1 cup water
1 cup sugar
8 inches Douglas fir (cut into 1-inch lengths)
1 cup water
1 tablespoon gin

Boil first cup of water with sugar and Douglas fir for 10 minutes. Strain and cool. Add second cup of water and gin. Churn as directed on your ice cream machine.

Recipe for a good gin-tasting party:

1.) Print six, glass-sized circles on letter sized paper. Label each circle 1-6
2.) Place six glasses on the table. One on top of each circle.
3.) Pour a shallow glass (about 2-3 swallows) of each gin. I recommend in no particular order:

Gordon's
Hendrick's
Old Tom
Voyager (locally produced in Woodinville and AWESOME)
Plymouth
Dry Fly (Personally, I hate it. But others seem to like it.)
Bombay Sapphire
Tanqueray

The trick is to include both cheap and expensive, well-known and obscure brands. Keep your guests guessing.

4.) One-by-one, work your way through the gins, sipping water between each glass. Also, keep a handful of coffee beans handy to refresh your sense of smell as gin can be quite odiferous. For each glass, have your guests make notes about what they taste.

5.) When it's all done and everyone's picked their favorite -- you'd be surprised what tastes good when you don't know how much it costs -- start mixing cocktails!

When cocktail time arrives, I recommend having a few common mixers handy. Besides the traditional gin-and-tonic, I'd recommend:

Aviation
2 shots gin
½ shot lemon juice
⅓ shot Maraschino
⅙ shot Crème de Violette
(optional egg whites)

If that doesn't satisfy your tastes, try the Cocktail Database!
http://cocktaildb.com

Dear everyone else who answers this question:

While I'm sure you answered with the best of intentions, you are respectfully wrong ;)

The finest bourbon in the world is unequivocally Pappy Van Winkle's 20 year bourbon. It's smoother than the 10 year, but not quite as mellow as the 23 year. It has a unforgettable wisp of vanilla scent that wafts inches from the bottle's nose. If any scotch drinker tries to snub their nose at you ("waahhh... scotch is just sooooo much more complex"), you can hand them a sifter of this elixer and put all arguments immediately to rest.

On the other hand, it's also very difficult to find and usually over $100/bottle. So, yeah. Evan Williams is a good well.

I second the opinion of the featured guests, Kathy and Paul. When it comes down to it, jams & preserves are basically just fruit, sugar and gelatin... so you can substitute them just about anytime a cocktail calls for an analogous liqueur.

If you want to gussy-up your cocktail a bit: get a ketchup squirt bottle, fill it with a gooey jam or chocolate syrup, then make a swirl in your glass. The sweetener will stick to the side of your glass and make for a fanciful decoration.

I hope this answer isn't too too pedestrian, but have you considered a bloody mary?

Vodka, tomato juice, beef broth, strong horseradish (none of the "creamy" @#$!), Worcestershire sauce, black pepper and your choice of pickled vegetables to liven up the affair. I, personally, prefer to rim my glass with a mixture of garlic salt, celery salt and kosher salt.

Switch out wasabi for horseradish and you have what most people call a Bloody Dragon.

Switch out tequila for vodka and add a dash of agave syrup and you have a Bloody Maria.