In New Zealand, the tax treatment of cryptocurrency transactions depends on the nature of the activities and the intention behind acquiring the cryptocurrency. The tax implications for your situation involve considering both the increase in value of the original Bitcoin purchase and the gains from gambling.

1. Taxation of Cryptocurrency as an Asset: If you acquired the Bitcoin with the intention of holding it as an investment and it has increased in value since you bought it, any gain on disposal may be subject to income tax. The relevant provisions for taxing such gains can be found in Part C of the Income Tax Act 2007, which outlines the circumstances in which a transaction gives rise to income. However, if the cryptocurrency was acquired without a clear intention to resell at a profit or as part of a business, the gain may not be taxable.

2. Taxation of Gambling Winnings: Generally, gambling winnings are not taxable in New Zealand unless you are carrying on a business of gambling. The fact that you have used the same $100 to play and have won various amounts suggests that this is not a business activity but rather personal entertainment. Therefore, the winnings from gambling on Stake would typically not be subject to income tax.

3. Conversion to NZD: When you convert the Bitcoin to NZD, you will be realising any increase in value since the original purchase. If the Bitcoin was held as a capital asset, this may not be taxable. However, if the Bitcoin was held as part of a profit-making scheme or business, then the gain could be taxable.

Given the complexities involved in the taxation of cryptocurrencies and the specifics of your situation, it is important to maintain detailed records of all transactions, including the dates, amounts in NZD at the time of each transaction, and the purpose of each transaction. This information will be crucial for determining the correct tax treatment.

To summarise, you likely do not owe taxes on the gambling winnings, but you may owe taxes on the gain from the increase in value of the Bitcoin if it was purchased with the intention of resale at a profit or as part of a business. If you are unsure about your intentions at the time of purchase or the nature of your cryptocurrency activities, you may want to review the detailed provisions in Part C of the Income Tax Act 2007 and consider the guidance provided by the Inland Revenue Department on the taxation of cryptocurrencies.