Ask HN: What linux distro should I start with?

I just got myself a used Fujitsu Lifebook E8410 - the thing's around 6 years old, maybe older. I'm aiming to use it to learn C and wanted to install a gnu/linux on it, but I don't know where to start. A gui would be nice though, maybe not even a DE, I might just put i3 on it.

I've used debian before, but I'm open for any lightweiht distro with support for older hardware.

I'd love to hear your recommendations and/or warnings.