I want to learn to root. What's the easiest phone to start with?

I want to learn to root. I bought an unlocked Nexus One to try it on. But thought I'd ask if there's an easier phone to start with? Or is that one good? It's never been used. It's Android version 2.3.6. GSM... I have to phone numbers, Verizon unlimited grandfathered plan with a Samsung s5 & an AT&T Go Phone with a broken HTC One. I don't care which carrier I use & no problem to get another one if that's better. Any ideas? Bill