I have a monthly budget that covers makeup and beauty-related expenses. There are months that I go over but I either "pay it back" in future months or just know that I went over-budget and that means I have that much less to put in savings. Having a monthly budget, for me, means that I carefully weigh my big purchases, plan to stock up during F&F sales, Chic Week, and so on, and know exactly when I have money to splurge because I feel like it.
I re-evaluate my budget based on the previous year's expenses once a year. If I was always far under for a month's spending, then I adjust it down. If I was always over, I might adjust it up or look at what I was spending it on. (Budgeting software, it makes all of this possible.)
I'm not super-comfortable talking dollar amounts but I will say that I have a "no credit on beauty supplies" rule. I don't want to max out credit cards on beauty products. I will only spend from my bank account - or in the case of Nordstrom, where they have a reward program, I spend on a Nordstrom card that I immediately pay off.