Simple answer is to start selling. Get revenues in, however you can and defer costs or delay paying bills (in agreement with your suppliers).
Grow the business slowly – only spend money when you have already made some money.

This is not an easy path to take and so I”m going to make a suggestion for an alternative route.

1 – Start by building a list of people who are interested in what you are doing
2 – Write to them regularly about how you are progressing on your journey towards starting your business so they stay interested
3 – Ask them to help you out e.g. recruit their friends to your mailing list, like you on social media, publicise your journey / mission
4 – When your product is ready to launch, test it first on your friends in the mailing list
5 – If you haven’t got it 100% right, they will forgive you because they are your core friendly audience. Go and improve the product / service and come back to them again (and again, and again if you need).
6 – When you’re finally ready for the full public launch, ask your friends if they’d consider buying in bulk, in advance – so you get enough money to pay for your manufacturing / sales costs and some advertising to prime future sales.

This model is what Kickstarter and Indigogo popularised – the crowdfunded model. What I describe above doesn’t use their platforms, but you could.

Here are more resources you may find helpful

The ultimate guide to crowdfunding in New Zealand

NZ crowdfunding platforms PledgeMe, GiveALittle, Boosted.

If your idea is good enough, you could also consider Equity crowdfunding – SnowballEffect is a kiwi specialist in this. But they mostly work with established businesses.

There are also regionally based organisations who can help you get started using local government funding to pay for professional advice to shortcut your learning.
https://wheelhouse.org.nz/about-us/ in Taranaki
The Icehouse in Auckland
Soda in Hamilton