Their relationship: Oh, Tristan. So spoiled, so obnoxious. He's private school snobbery in human form. Tristan doesn't quite know what to make of Rory — the shy, brilliant new girl at Chilton who seems immune to his smarmy charms — and that's what hooks him. Tristan can't have her, so he wants her even more.
Why he's important: At heart Tristan isn't a bad guy, just a product of his privileged environment. He's also at the mercy of his parents, who take him out of Chilton in season two and send him to military school. In the end, he's the kind of guy who we all know would be exactly wrong for Rory — but their dynamic also shows the audience that Rory won't simply be swept off her feet by any guy who smiles at her.