I dunno, if you're really short on space your best bet might be to use it for decent glasses and a shaker, spoon, measurer, etc. and just get your liquor and mixers ad hoc.

I'm still looking for the perfect cocktail glasses myself; Crate and Barrel has nice (if huge) Double Old Fashioneds and so on, but their "Martini" glass is enormous, like 16 oz. or more, which is about four times the size you want for a Martini. Otherwise it just gets warm, and since a Martini is close to straight gin, do you really want to carry around a pint of warm gin?

I found some at Daiso, the Japanese dollar store in Westlake, that are cheap and nasty but functional and appropriately sized, maybe 5-6 oz.

For essential ingredients besides your base liquors, like, say Triple Sec (for margaritas), you buy it when you need it the first time and then you'll have it around for the second, third, fourth -- if you're going through a ton of Triple Sec you're doing it wrong! But you need Triple Sec (or Cointreau, if you prefer).

Vermouths (French for Martinis, Italian for Manhattans) don't keep all that well for long periods, even though my dad had the same bottle for twenty years. Keep them in the fridge and use them up within a week or two at the most.

Get some bitters -- Angostura and at least one other, like Peychaud's (for Sazeracs), Fee's Orange, or cucumber. Small bottles, don't take up much room. Another thing to keep around is simple syrup -- heat equal amounts of white sugar and water until it's dissolved, then pour in an old empty bottle. A quart will last a long time. Or, get funky and use Agave Nectar -- your supermarket has it.

Then, if you're having a party, get the base liquor, mixer, juice, and fruit on the day.

If you have room, you can keep some basic liquors that you don't drink much yourself, whatever that would be. Vodka is vile but a fair number of your friends are going to want it. After that, bourbon or rye (rye is cool for Manhattans, and if they ask for just bourbon rye will be acceptable) gin and rum are your biggies for mixing. Someone will always be happy to see Scotch. Good tequila is fantastic stuff (only if it says "100% Agave" on the front of the label, though), but you may not have anyone who wants it. Brandy likewise.

For soda water, the best thing is to get some of those little Hansen cans and stash them somewhere. Nothing is worse than that old two-liter bottle in the back of the fridge that turns out to be flat when you open it; unless you're serving a huge room soda will ALWAYS go flat.

If you want to impress gin drinkers, a four-pack of fancy-pants tonic water (for G&Ts) from Fever Tree or Q Tonic can also be stashed in the back of a cupboard, instead of boring old Schweppes or Canada Dry. Again: small bottles. Big ones go flat. Flat tonic is gross.

You should learn a handful of basics -- Martini, Manhattan, Margarita, Daquiri. Scotch and soda, bourbon and soda, gin and tonic -- these aren't really recipes, you just pour it in.

You can't really store fruit or juice; buy it when you need it. You can store lime juice but don't, use fresh-squoze.

Most important: make sure you've got everything you need to make SOMETHING. If all you've got left is a bottle of bourbon and some tonic water, you don't have a bar, you have a crime scene. If you have gin, make sure you've got vermouth and tonic, and so on.

Wait, I take it back -- most important of all is LOTS OF ICE. The best drink in the world is a healthy tot of quality rum over a couple of ice cubes.