Rather than try to build out a bar with a broad array of options from scratch I recommend starting out more narrowly. Focus on one or two families of drinks at first. Things made with the same type of liquor. For example, margaritas. Or piņa colada. Both have lots of variations. Invest some time-- and money!-- learning how to make each drink really good by choosing the right liquors, the right mixers, and the right technique to combine them. Start with something you enjoy so you bring passion to the effort. As you develop something special with one type of drink, begin adding the next to your repertoire.

The start-narrow approach works for entertaining because most drinkers, in my experience, are willing to try whatever category of "house speciality" I'm offering. Most people respect the effort that goes into making a good drink, not a merely serviceable one, and are curious to try it out. Sure, there are some people with set preferences. Like the guy who "only drinks Scotch, and then only single malts". Or the gal who's like, "Nah, I just want a glass of Chardonnay." You can keep some basic bottles on hand for those folks. But recognize that they're special cases. You don't have to be all things to all people.

The result of the start-narrow approach is that your friends will come to see you as a person with taste and skill in serving drinks. Not just a person with a lot of bottles on the shelf. (Anyone with a shopping list and a credit card can assemble a reasonable collection of bottles.) They'll be more likely to come to your parties in the future. They'll invite you to theirs. They'll talk you up amongst friends. They'll even bring good bottles as gifts because they recognize your passion to pour a fine glass, not merely one that "gets the job done".