Like you, our first year had a few supermarket plastic baubles and some donated by DSis when she moved house beforehand.
As this is our 21st year, while we still have the original tree, we upgraded that for a newer fake (prelit and taller) last year. I gave away the original baubles a few years ago, between various DSiblings who moved and needed some for themselves, and then a bag to a charity shop.
We have a lot of individual ones that we have made or bought on trips worldwide over the years. I still have about 4 of the extremely precious ones we bought that 1st Christmas (about 12 glass balls and drops from Primark, where I also got the tree - but quite interesting ones that I really love).
2 years ago, I had actually realised I had a lot, and started trying to put together a red/gold/green more traditional set (mostly already what we have) and a second more modern set (blues/silver/white, with turquoise, pink, lime green etc) that I was going to put on the original fake (we had a real tree that year). It didn't happen, but I have now gathered a few more bits to make that bluer tree (mostly decorations like robots, astronauts, log cabin, and lots of marine life things - blue whale, jellyfish, other fish etc) come to life this year in the kitchen/diner.
I probably should stop buying new decorations though, even when I see ones that are lovely...this year I only bought things for flower arranging purposes.