I have 2.
1. When I saved for a super long time and bought a magical chokato chia pop and morphed my chia into a chokato. That was all legit btw. But it was the most expensive thing I ever bought (before number 2 below happened) and it wiped out my bank completely, but I was so happy. I just love chokato chias so much, for some reason I find them funny to look at.
2. This moment is 2-part and spanned a couple months so okok it's not a 'moment' but whatever. Part 1 was when I finally got me a pirate draik egg and hatched me a draik. Part 2 (OMG YEEEEAAAAHHHHH) was when I painted her Eventide from a very lucky FFQ which I'd saved to paint her. That was the only FFQ I'd ever gotten, but it got me my Eventide Draik and I'm still happy looking at her.
Unfortunately I paid a hell lot for the draik egg since I got them when they were still quite expensive. I think they're much cheaper now, but I don't really regret it