My first Linux was Gentoo. It took several tries to get code compiled and working on that Pentium 4, but I will say, the process taught me a lot about Linux in general. It was the ultimate crash course. I’d recommend Gentoo for all beginners who don’t mind digging in to the point of frustration, because it’s a great learning experience.

This is literally what dd does and what I would have recommended, if this person hadn’t beaten me to it.

However, if you’re cloning to another disk or partition that will be plugged in at the same time as your existing installation, you’ll wind up with two partitions with the same identifier — a recipe for eventual disaster. In that case, I would run through setup (with your current disk unplugged) and then rsync over the new root partition.

I’ll second Debian. I run it on backports and it’s reasonably stable, but if you want it rock-solid, don’t do that.

You might want to keep your browser more up to date than the rest of your OS. That’s up to you as the user. Mozilla has a deb you can add to Apt manually, should you choose.