Hi, Lucky you! Turkey is my favourite place.
I would say that it depends slighty on what part you are going & if you will be eating out & paying for drinks a lot.
It is cheap there, I am 23 & drink loads when i am there so i would take about �150-200 for a week, but that would be mostly for food & drink. (that doesn't include any excursions). Hope you have a nice holiday!
& you might want to take extra for the cheap clothes & lovely jewellery that they do!
another thing is i wouldnt bother changing too much money into turkish million ( cant remember the name sorry ) as i found they would rather have ten pound notes makes it easier for you not having to change money back and lose anything on the amount .