Slytherin students speak with Ominis Gaunt, Sebastian Sallow, and Imelda Reyes. If you are sorted into Ravenclaw, you'll introduce yourself to Amit Thakkar, Samantha Dale, and Everett Clopton. These conversations won't make you better or worse friends with these characters, and everyone will be met eventually during lessons, quests, or dedicated friendship missions regardless of whether you meet them on your first night.