Depends on how many nights you are going to hit the bigger clubs and which nights/clubs. Pacha for example is considerably more expensive than Sankeys, but both are obviously more pricey than the West End. I'm personally bringing 150euro per day.
Some tips:
- Buy alcohol in the supermarket and pre-drink in the hotel, or even better, hit the rocks at Mambo.
- Buy some baguettes or easy to make food for the apartment so you don't have to buy lunch/breakfast.
- Take the Discobus when travelling to bigger clubs.
- If you know what events you are going to, buy tickets in advance.