My biggest regrets is not setting up a personal tracking system in Excel or something so I know which pins are the ones I bought myself, direct from Disney or source vs CM trades vs trades with other people. So I would have provenance I could refer to and have confidence in which pins are authentic. Plus, and inventory not reliant on online databases.
Second, assuming I couldn't get a pin. When pin trading started I lived in Washington state, and had infrequent trips to either DLR or WDW. It meant I had to be realistic about what type of pins I could obtain without being a big spender. This has served me well. FOMO is really easy to let get out of control which brings a lot of negative energy into collecting. I still just pretend most WDI / DEC (WDCS) pins don't exist as far as my collecting is concerned. However...
There was another collector who used to post here who had a goal of collecting all the Disney Auctions Stitch pins. A massive goal for those who know the volume and costs associated with that. But the years I watched her ISO list dwindle down without the sense she was throwing insane money at it. Slow and steady, within her means. When Frozen was released it was super, super hot. I am a winter solstice baby, so I have an affinity for the designs, the colors, the icongraphy (less so the actual story, funny enough), but after watching the Stitch quest, I decided not to be daunted by the difficulty. I kept plugging away, jumped on sales when Frozen collectors "got out because it was too expensive to be completionist." And now I have a pretty sizeable Frozen collection, with a lot of the early HTF pins.
On a similar note, I've always collected Figment. At the beginning he was one of the most popular characters and now he is one of the most popular characters for park people. In the middle, though, he ebbed and flowed. I did a good job of trying to keep up with new releases but I never spent as much time as now think I should have on tracking down stuff from the early years, or event stuff. During Covid, I made him a focus and picked up a lot of great pins at prices I was comfortable with, and I found myself asking, "What if I had been doing this the whole time?" Instead of thinking there was a group of Figment pins, I would just never own.
Sure, there are not a lot of recent grail quality pins, due to my limits on what I am comfortable spending on a single pin. But for those that are willing to spend more there have been opportunities to buy some of these at "not peak price." Slow and steady, and your collection will blossom.