I've found that the greener oolongs are a good introduction because they contrast so well from any tea that they've had before. They are very easily accessible, but then as one refines their tastes these oolongs also have more to offer. The Taiwanese jade oolongs have a lot of up-front characteristics that appeal to the new drinker, such as aroma, taste, and a thick mouthfeel. Later, however, you might notice the aftertaste, "after-aroma," and the way that it affects the mouth, throat, and body afterwards.
IMO there are better options than Adagio. Hou De has some of the best, though it can sometimes be difficult for a beginner to accept some of the prices. Even his low end ones are fantastic, though, so I'd say to check out Hou De. His prices are worth it, but if you just can't bring yourself to spend that much quite yet, then you could also check out FloatingLeaves.com and TeaCuppa.com. Floating Leaves has machine processed Jin Xuan and Four Seasons that are inexpensive and still quite good. Any of their others should be good as well. TeaCuppa's Da Ye is a good one (a Chinese tea that is similar, in some ways, to a Taiwanese), but I've never had a bad experience with anything from them.