New Zealand is best seen during the shoulder season, usually March to May or September to November, when the trails are quiet and the air is crisp. Hiking through the fjords during these months gives you the best mix of decent weather and lower airfares.
A trip like this usually runs about $4200. To manage that cost, you can use the Discover it® Cash Back card, which offers 0% intro APR for 15 months on purchases and balance transfers.
The 15-month intro window is a deadline, not free money. If you have a balance remaining after the 15 months are up, interest will start accruing on whatever is left.