which topic is popularly in your area.
When I begin with a student, I use Nursery Rhymes, Song Lyrics, Poems and short and simple essays for English Practices.
I also think that trying to engage in spontaneous dialogue, with another person, is a very
limiting and restricted method for improving language skill
I do offer some chances for students to engage in spontaneous dialogue, but only after they reach the point of confidence when working with me.
One of the things that you notice about people sort of just "making friends" for English practices,
is that you read so little about the method here. I think it is fact, that most people who try do do this, eventually just drift away. The reason is that although the foreign student of the language may become less nervous and more confident over time, their actual vocabulary and language skill remains only at the level of casual conversation, at best.
So for a "subject" your language partner should show you some sort of printed text
( by e-mail or posted on Skype ...etc.) that serves for either reading, pronunciation exercise, or general discussion.
Also, the students who seek out these kind of "chat" lessons, also seem to Come---and---Go rather quickly. Perhaps they suppose they have exhausted the method for practicing English, when in fact, they really have hardly begun to practice English.