I tend to order in bulk, so my orders don't get placed every month- but if I were ordering monthly it would mainly be waxing supplies. Lycon azulene hard wax (not cheap), deplieve pearl rosin (I try to stock up when Cosmoprof has it on sale for $9.99 vs $14.99- big savings), table paper, spatulas, bikinis and wipes from Universal.
Facial supplies usually last me longer- but I do find myself ordering Dermalogicas post extraction solution, massage cream, and colloidal mask base often and Glo's seaweed mask and lactic, as well as their pre peel prep and neutralizer.
More often than not, I'm purchasing paper goods, etc...Barbicide, cups, tissue, paper towels...gloves...that stuff.
I'm bringing on Rhonda Allison in the new year, so I'm sure my monthly orders will be changing ;)