That's a VERY big question!!!!
Do you know if the ladies prefer white, or red, or bubbly? If you just want to buy something to have fun - and to make it more of a wine tasting event - I would go with Pinot Noir. Try a California Pinot and a French Pinot. A Cotes du Nuit (red) can be had for around $20.00 and they can compare the difference in that and a California Pinot. One is fruity; one is earthy. Or, if they prefer "bubbly", you could compare a true Champagne (for around $40.00 - Duval Leroy comes to mind) versus a Cava and Prosecco. There is one from New Mexico bottled by Gruet that is wonderful and has a granny smith apple note to it.
There are so many choices here that we REALLY need to get it narrowed down to white, red, bubbly, or varietal i.e., Pinot Noir, Cabernet Sauvignon, Syrah/Sirah/Shiraz, Trebbiano, Chianti, Pinot Grigio, or region, i.e., Spain, Italia, Austria, Australia, Germany, France, Alsace, etc., etc.
So many wines, only one liver................