My first was an Ibanez GIO POS that my parents bought for me, along with the world's lousiest 35w combo amp.
I put Rotosounds on it and got to play through a good amp once. The tone was powerful and growly, and that's when I finally started trying to master the instrument.
Once the amp finally broke, I couldn't afford to buy another one, so I 'played acoustically on and off for a while. Eventually I traded the bass in and got a good price. I think it shaped my preference for thin necks.
These days I gig with a Fender Jaguar. I always practice with an SX PJ, which is a different animal but feels and sounds 70% as good as the Jag, which is still 10 times better than every other bass I've had except that magical Jag.