If there's a better lifelong-learning topic than wine, I've yet to hear about it.
It's a realm that's both wide and deep, affording opportunities to delve into geography, geology and especially history. It's a domain filled with fascinating people worthy of their own biographies, whether they be seventh-generation growers in Spain or self-taught vintners in Walla Walla.
And there's the wine, so much wine, so many grapes from so many places. It's great fun to check out relative obscurities such as assyrtikos from Santorini and tannats from Uruguay. But it's perhaps a better learning experience to figure out which renditions of the more available varieties you prefer. In general, that can be done continental-style: in side-by-side-by-side samplings of the same varietal from different land masses, preferably in the same price range.
Yes, geography matters. On our shores, California is a beacon of sunshine and, as a result, fruit ripeness. Meanwhile, most European countries have cooler climates, shorter growing seasons and often a good bit less sunshine during those seasons. Which means less sugar/lower alcohol (again, in general) and more of a balance between fruit and acidity.
These sampling endeavors will be entertaining as well as edifying, as they entail convening with friends to scope out a variety of wines of similar types. I have selected readily available wines that not only are exemplars of their grape and place but also won't break the bank, falling almost invariably in the $10 to $15 range. These are all bottles that I've enjoyed thoroughly over the years.
Sauvignon blanc: Giesen is the epitome of New Zealand sauv blanc, with soaring grapefruit notes and a racy texture. Ditto Pomelo as a paradigm for California: ripe fruit, super-smooth from start to finish. Domaine du Rin du Bois Touraine carries the flag proudly for France's Loire region, with lively flavors and lovely fruit/mineral/acid harmony.
Chardonnay: There's less geographic diversity here because a more important distinction is between the buttery, oaky style (which has been toned down in recent years) and the purity of unoaked chards. I've been enjoying the J. Lohr Arroyo Seco Riverstone for decades; it's plush, rich and spicy on the nose and palate. Four Vines "Naked" is just as lush on the nose and fruit-packed on the palate but with a crisper finish. The Les Chenevieres Mâcon-Villages combines Old World restraint and slate with polished fruit flavors.
Pinot gris/grigio: "Gris" is French and made mostly in Alsace, with the Hugel Gentil's Alpine-flower aromas and green-apple notes representing it deftly. "Grigio" is Italian, and the lemon-lime-y Cantina Tramin Sudtirol beautifully transforms from bracing beginning to silky finish. Oregon generally goes with "gris"; Benton Lane is a bright, zesty delight with late-breaking oomph. Estancia, like most of its California peers, uses "grigio"; it's tropical through and through, evoking the spices and the fruit of warmer climes.