Unfortunatly as much as you can....
Take your cash and credit and debit cards, I took a lot of money when I went as I go on most/all the optional extras, I allowed for many extra flights helicopters etc but in the end only managed to do one helicopter up the Franz joseph due to weather conditions, also when I went 3 years ago the tour manager had more things we could do once we were out there, I paid over £100 for extras in HKG and there were 2-3 extra in NZ, one being a winery tour that was £ 70ish so just bare in mind it might not just be what's on offer there might be other things that either you choose to do independently or the manager mind source.
It's a great tour you will see so much and have fun.
I am sure I left a review when I came back I went Janaury 3 years ago.
Cindy