Too many.
I'm another kindle 99 p special hoarder. I have hundreds of unread books and would probably not run out of books if I didn't buy another book for the next 10 years.
But the way I see it is that I'm not spending any more on books, I'm just getting more books for the same money. Instead of buying one £5 book a month, I'm getting 5 x 99 p books a month, they're the same books, I just use ereaderiq to track when they go on offer and buy them then.
A few times a year I go and get a few of the mini packs from Hotel Chocolat just for me. I don't generally buy 'normal' chocolate day to day, so would rather have a few very nice and expensive ones every so often, than something like a Mars bar every day.
But both of those are dwarfed by the thousands of pounds a year I pay in exchange for fresh air and for someone to take me out to sea and watch me jump off a perfectly good boat (scuba diving).
Buying nice things for yourself is never a waste of money if it brings you pleasure and you can afford it out of genuinely disposable income, ie after bills are paid, savings put by for the short and long term and food and travel etc are accounted for. So no reason to feel guilty.
It makes me just a little cross that men seem to get away with spending hundreds or thousands on their hobbies and interests, but if women spend money on themselves it is seen as frivalous or wasteful.