I have a D3000. The heck I'd ever buy an expensive flash for that thing. As a matter of fact, it was my first camera, and I bought a Youngnuo for it, and it served me well. The Chinese flash went with me to a D90 and then a D7100, which I then upgraded to an SB-600 back then, which the Youngnuo was more than enough for what I was doing at the time. I was shadowing a Fortune 500 corporate events pro at the time, and he told me to go buy a diffuser for the Youngnuo while I was using my D7100. He didn't knock it once and was impressed by its performance. He would have us shoot side by side with his 5d II and no one would know the difference.
If I was ever to shoot as a pro, I'd shoot top tier, branded gear, just because they've saturated the market, which allows all of us to understand their reliability better than the off brands. Heck, I'd shoot off brands if they sponsored me and gave me backups. But as an amateur, I would go with an off brand all day long if I was on a budget. I'm fortunate enough to buy what I want, and that's why I have an SB-910 and all Nikon gear. Does it allow me to take better photos than when I first started? Nope. I do photography as a love hobby (not as a pro or an amateur), so I will shoot personal events for friends, family, and strangers who are not fortunate enough to hire a professional who is truly passionate about photography, and the SB-910 carries me a long way on that end. I use to have people rent the gear for me for their shoots. Now, I can just charge in beer and liquor.