Clothes are fripperies for adults who have a reasonable selection of clothes that fit, are in good condition and are suitable for the circumstances that we find ourselves in, which is a position that most of us are probably in.
I think we're just using fripperies as shorthand for anything that's non essential and I don't think the OP is talking about spending her £500 every month, more about separating this money out as an affordable amount she can spend without worrying that she's not saving for essentials.
If it's not spent, it can roll over until it's needed. Some time in the future she might decide to buy an expensive piece of hobby equipment, or a good coat and boots for winter or something else where £500 might not be enough. And because she'll have a pot of money available, it will allay the 'can I afford this' worry. If you want something expensive and have a pot of money available, you can afford it.
We pay for joint holidays and meals out from the joint pot, and anything we do ourselves/with friends out of our own spending money. Presents for family come out of joint money, but we don't buy much, we don't really exchange significant gifts with anyone.
My money goes on posh gin, lunches out, kindle books, odd spa day just to sit in the hot tubs mainly, occasional diving trip away or diving kit, some clothes, but not many, I have far too many because I never throw anything away. I don't spend anything on hair, make up or treatments.