I buy all my wine when it is on special offer at supermarkets. Tesco, Supervalu and Dunnes all have drinkable wines on special offer all the time.
You have to take the “Half Price” offers with a pinch of salt, but the wines that are sold as “half price” are generally worth the reduced price. They are rarely worth the claimed unreduced price.
You can buy very drinkable wines for €6-8 from all the big supermarkets. Supermarket wine is a lot better than most people give it credit for.
Avoid Vin de Table, in fact avoid any French wine under ten euro a bottle. French wine is grossly overpriced. Avoid Lidl (TM) and Aldi (TM) wines – they are cheap butonly fit for adding to punch or for cooking with, they have no bouquet and always taste rough.
Be careful buying Rose wines. Californian Rose is wonderfully light and many Spanish and South American Rose wines are designed to look like Californian ones. The imitations are much heavier, they do not have the light and fruity character of Californian Rose.