Naomie and Anneri !
I second
Anneri, " La Petite Robe Noire " is quite common but some Guerlain perfumes are must-haves such as l'Heure Bleue, Vol de Nuit, Après l'Ondée, Shalimar.... L'Instant is very good too IMO, Jardins de Bagatelle too, and Insolence is a masterpiece.Champs Elysées is very nice too. If you love oriental warm perfumes I would recommand Shalimar if you love floral ones Insolence eau de parfum ( the eau de toilette is much more "violent", really powerful), Champs Elysées soft and lovely, Jardins de Bagatelle more intense and powerful. If you love rose scents you might like Nahéma too. Jicky as Anneri mentioned it is a true masterpiece, created in the 19 th century as many other famous Guerlain perfumes.
Definitely worth the price Naomie