@Chasingsunsets That's a great start to coin collecting. It's awesome that the Sydney Olympic Coin holds some sentimental value to you. That's fantastic.
When I purchased coins, I buy ones that remind me of times in the past. For example, I purchased the 2023 $5 Beauty, Rich & Rare - Twelve Apostles Domed Silver Proof Coin because it reminded me of the holiday that my mum and dad took me on when I was about 12. And they only took me, and not my two sisters. So it was extra special and I really enjoyed stopping at all the different spots along the Great Ocean Road.
And other than coins reminding me of the past, I also like coins that I find pretty, but I try not to go overboard. And I keep changing my mind as to what sort of coin collection I want to build, so when I leave it to my daughter when I pass, will she be able to sell the coins at an increased price. I just looked at how many coins I have entered into the Numista Database, and I currently have 610 coins. And I still have a lot of coins to add. Lol
You should take a closer look at the flag on the 2000 Millennium 50 cent coin, as it looks a bit different to normal in the photo (or it could be the angle the photo was taken on). This is what an incused flag looks like. If it is incused it could be worth around $20-$30, while high-grade coins have sold for over $1,000.

I also have a collection of the 2006 50c XVII Commonwealth Games coins in cards. I have about 5 so far, but they are not cheap to purchase. So, I just keep an eye out in the auctions, to see if I can pick up some a bit cheaper.
I also love the Ocean Series. I have been bidding on a few different sets at auction, but so far I haven't had any luck.