It's a problem the everybody faces eventually, how do you go about stocking your bar? The answer I have, may suprise you a little bit, but frankly I think it is the only one that makes sense.
One of the most common questions I get, is "I'm trying to set up a home bar, what liquors should I buy?"
Perhaps the most correct answer here, is "Go to your nearest liquor store, and buy one of everything." However, in most cases I doubt this is the answer the person is looking for. This solution would not only be quite expensive, but it would also take up more room then I expect most home bar areas would have. However if your goal is to be able to make any cocktail that one of your guests might ask for, this is unfortunately what you probably have to do.
I doubt that anybody is really trying to set themselves up to make any imaginable cocktail, instead they are just wanting to have the makings on hand for a decent variety of drinks that they can serve. Fortunately, such a home bar is easier and far less expensive to shop for. The key however is still knowing what to buy. This shopping list is far more difficult for me to provide, especially with such an innocent and simple question for starting with.
A minimal shopping list that I would arrive at for my home bar would most likely be a lot different then what you, or many others might select. This is all based on the types of drinks I like, and how these might differ from your favorites. Instead of simply laying out a shopping list, let me provide some guidelines and assistance in helping you to work up your own.
Your Three Favorite Cocktails
First, select your three favorite cocktails. Make sure you know the recipes for these, as well as how to make them properly. Your first shopping trip should probably focus on simply getting the ingredients you need for this.
If you are asking this question, it usually also means that you don't have a lot of experience or knowledge about mixing cocktails. Assuming that these are drinks that you have learned to love at some local bar or cocktail lounge, you should make it a point to chat with the bartender a bit to find out if they have any tips on how they make them. You shouldn't assume that they use the same recipe that you might find in whatever recipe book that you have, many cocktails have a subtle (and not so subtle) variations that might be used.
Now, just spend some time perfecting your process for making these drinks. Eventually, you'll be able to make these as good, if not better, then the bartender can. When friends now come over, you'll be confident in your ability to provide them with a great drink.
With these three cocktails under your belt, and in your cabinet, you hopefully have a start towards a collection of ingredients for other cocktails. Your next step will be to try to identify some other cocktails that can utilize some of these ingredients. You can either browse through a cocktail recipe book (or web site) and try to locate some other cocktails that can be made with what you have on hand, or you could spend a little more time with your local bartender (during a slow time at the bar) and see if he has some ideas on some other drinks you might be able to make. Of course you'll order some of these drinks from him so that you can determine if they are ones you might like to add to your repertoire.
Again, you should perhaps try to select three cocktails to add to your collection of recipes. And don't work hard at making sure that these new cocktails only need what you currently have on hand; remember that the goal here is to build up your liquor cabinet. You should try to make sure that you need to pick up a few more ingredients, especially if they are semi-common ingredients that other cocktails will use.
While there are most likely several items missing from the current contents of your home bar, you've at least now got 6 different drinks that you will be able to make for your guests. Most likely, there are probably several more that you'll be able to make as well. It doesn't take too many ingredients to be able to make a wide variety of cocktails.