The first instrument I ever bought was a recorder (the flute, not the device). I believe my sister may still own it - and she can keep it, I enjoyed it when I was a kid but can't stand them now! I had lessons for a while when I was about 7-8 years old, but quit at the end of primary school and never laid hands on it since.
The earliest instrument I bought that I still own is my Squier Affinity Strat that I bought new in 1999. It's a very basic beginner guitar, finished in 3-colour sunburst with a white single-ply pickguard which is now very yellow from age (I don't smoke, nor have I ever). I've modded it with 3 Gary Levinson pickups from a Blade R2 Strat with 3-way switching between the bridge and neck pickups, and a second 3-way switch that adds the middle pickup in either series or parallel for a total of 9 different sounds. I also added Gotoh tuners, a Graphtech nut and Graphtech stringtrees. It's a fun little guitar, but it hasn't left its case in years,
The earliest bass that I still own was the 3rd I ever bought (out of around 30-40), a beautiful handmade 5-string by Dutch luthier Ellio Martina that I got used in 2006 (it was built in 2002). It was my main bass for several years, and it's the one that will outlast them all if I ever were required to downsize. It's incredibly comfortable and has a vast range of sounds, from somewhere between modern Jazz Bass to more hi-fi active sounds. It's not my main bass anymore (my Status S2 Classic headless 5-string is) but I'm unlikely to ever sell it.