I'm wondering about just that, I want to have a minimal model with little overhead that I can train to a specific body of texts but it doesn't need to know abou

I'm wondering about just that, I want to have a minimal model with little overhead that I can train to a specific body of texts but it doesn't need to know about all the rest. So basically it should be good at conversation and able to learn what I teach it, nothing else. But I'm having trouble finding resources about how to achieve that.