Check out your local Toastmasters club. Public speaking is part of it, but meetings also feature conversations on a topic.

For me, taking improv lessons helped a lot. It forces you to focus less on trying to be funny (or eloquent) yourself, and more on paying attention and reacting to your scene (or conversational) partner. Doing so in real-time helps with recall, which should unlock (useful) vocabulary, connections, and ideas.