This is a matter of preference. There are all kinds of flavored and sweetened liqueurs out there to try, look into some drinks that use a liqueur and your favorite spirits. A couple to consider would be a bitter liqueur (amaro) like Campari, orange liqueur, coffee liqueur, or even amaretto.
If you want to be able to mix up some drinks at home, you will want to be sure to have yourself the above ingredients on hand. Once you get an idea of what types of drinks you like, you can focus on just having those ingredients. It wouldn't hurt to have all of the above if you want to share with friends.
Be sure to share this with anyone who might need the advice.