£5 max and if I an include the card in that then so much the better.
DD was invited to a lot of parties over the last year - probably about 15 or so. Anything more than a fiver would have meant refusing some invitations as I don't have the ££ to spend much more than I have done on gifts for dd's friends.
I did note that most parents' budget is a bit higher though when I saw what dd got for her birthday from her friends. TBH it made not a jot of difference - dd enjoyed receiving the gifts and opening them - the value of the contents wasn't an issue at all so her friends' parents could have saved some of their cash imo.