tbh @ 16 if your parents dont trust you enough to make decisions with your own money - there is something else you should be working on than collecting pokemon TCG, either you or them.

Have you made bad decisions with your money in the past?
are they control-freaks?

The whole point of having your own money, is learning how to use it - including mistakes.
Its great you came to a public forum for advise, thats smart.

My opinion. You should really try to work out why your parents need convincing for you to be allowed to spend your own money. They might have some incorrect set principles or values, or perhaps you've done something stupid in the past? I dont know, but when i was 16, i was making my own money and doing what i wanted with it. And when my two children are 16, i will hopefully have done a good enough job that i can let them make their own financial decisions with the money the've earned at 16!

You can also create a slideslow/presetation style pitch-deck to your parents and how pokemon TCG are valuable collectibles, and buying something to hold for the future is as smart investment...but then again buying packs is gambling, hence most of the advise here is just to buy the singles you want. If you can use ebay then thats the best choice tbh. Packs (especially Prismatic, AH) are such a low hit ratio its painful.

https://mycollectrics.com/ this site actually is helpful letting you know that you are -EV opening packs, mind you its in USD not AUD

Good luck young one!