Potlucks are a great way to get friends together and to meet new people. To ensure that there is a sufficient variety of complimentary dishes, hosts often assign guests to bring categories of food, like salad, entrée, or dessert. But, even with this level of guidance, dishes may not work well together. To help prevent that, and to introduce some variety, try hosting a potluck where everyone is responsible for bringing a dish from the same cookbook.
I like that this removes the pressure of needing to choose a good recipe, since there are a limited number to choose from. Plus, if the dish you prepared doesn't turn out, you can easily joke about how it was your first time making it. But, if it's delicious, you can add it to your repertoire. Either way, it's a good bonding experience.