We started a new system late last year as I was losing track of how much they were getting and I noticed that they were more careful when actually spending their 'own' money.
My 14 and 17 yo get £170 each per month.
That includes money for going out, make-up, perfume, etc, birthday gifts, Easter/Christmas presents, clothes, shoes, etc.
All I pay for is:
☆School uniform once per year and school shoes, although if they are careless and ruin them, they'd have to replace them too.
☆basic toiletries, eg, shampoo, pads, deoderant, conditioner. If they want fancier ones, or use them up too quickly, then they have to buy their own.
They're expected to help out around the house in return for this.
They went a bit mad and spent about £50 each on clothes in the first week as they've got contactless cards, so it's easy to spend it.
I've reminded them to save for Christmas, etc, but ultimately they need to learn to manage money for themselves. I won't be bailing them out if they run out of money either.