If he bought you a rioja, then you might want to return the favour with a good grande reserva (Rioja AOC).
The grande reserva AOC name means you can pretty much count on not buying a lemon (the AOC classification requires minimum time under oak and in the bottle in the cellar. No wine maker would waste barrel and cellar space on anything but their best new wines. Similar applies to Reserva and Crianza but less expensive (less time under barrel etc) – Stoner’s top tip for buying a drinkable wine in a restaurant, but obviously you realise you’re getting a powerful, oaked wine. Nothing refined like a Montrachet burgundy etc.)
It means youre less likely to run the risk of getting either an overpriced unknown wine or fleeced on a “brand name” overpriced wine.
And for the pedants I know its DOC in spain 🙂