As a "portrait", the first shot should just be deleted. Sent to the hopper. It has 0 engagement. Lighting is terrible. It's poorly composed and you never want a portrait where the only thing you can see in the eyes is the whites.
The second photo is leaps and bounds better and the lighting is largely improved, although the (yes I know it's a candid photo) lighting is harsh casting a shadow over the eye sockets. Still not a great portrait, but 1000x better than the first.
The last shot is great. Lighting is great. Subject engagement is great. Composition is great. Thumbs up. Do more of that.
The sigma and tamron lenses are now viable options. They're great lenses, but the nikkor lenses excel over both. The Nikkor 70-200 VRII is just amazing. My new nikkor 24-70 2.8 VR is awesome, but it has a lot of chromatic aberrations, it's the only lens I actually have to fix in post for this. Otherwise, it's amazing and it's so sharp. The VR works great too.
DSC_9640.jpg by KeysarPhoto, on Flickr
DSC_5639.jpg by KeysarPhoto, on Flickr