I just recently went down that same road, and as far as I'm concerned, the must-try's are:
Tea for Two, Mechant Loup, Dzing!, Fou d'Absinthe and maybe a couple others I'm forgetting...I'll come back if I remember
Chergui (if you can find it), Daim Blonde, Gris Clair, Ambre Sultan, Fleurs d'Oranger, and again, maybe a couple others I'm forgetting.
Like I said, I just finally started to feel like I had a good grasp on these two houses. Truthfully, I wasn't too impressed with L'Artisan, other than the T42. The Lutens stuff seemed to be pretty consistent - thick, super-sweet and spicy - aside from the other oddities like Daim blonde and gris clair.
I find Serge Lutens to be kind of overpriced for such small quantities (about $120 for 50ml). The L'Artisans are more reasonable at $95 for 100ml.
My top pick out of the whole bunch: Tea for Two.
Good luck and keep it under control!