As Dan and mattdm said, you get what you pay for, and it's a subjective decision whether the extra cost is worth the extra quality and features. A few comments:

VR

You will want to stop any of these lenses down to f/8 or f/11 for maximum sharpness. Outdoors on a sunny day that means 1/200th at ISO 200. This is near the limit for hand-holding at 200-300mm, so VR may be of use.

Autofocus

In my experience, the Nikon lenses autofocus faster and more accurately than 3rd party lenses. That seems to be a generalisation backed up by online reviews and feedback.

Coverage

I wouldn't worry about the "gap" between your 18-55mm and a 70-300mm, you won't miss any shots due to lacking 55-70mm. Zoom with your feet.

Upgrading

If you go with the Tamron or the 55-300m, and later on decide to upgrade to the 70-300mm, you'll have spent more than if you bought the best lens to begin with. It's not a mistake to be a less expensive lens - often people find they don't end up using it anyway - but if you know you will do a lot of wildlife photography and make good use of it, over a long period I think it's well worth the extra $$.

If you decide to upgrade, you can often sell the Nikon lenses at a premium to used 3rd party lenses. So for that reason I'd go with the 50-300mm over the Tamron if you were going with one of those two.

I haven't used the Tamron 70-300mm. I do have their 17-50mm which is an outstanding lens. But reviews of the 70-300mm say it's very soft at 300mm. I used to have the Nikon 70-300mm (non-VR) lens (which is optically nothing like the VR version) and it was horribly soft at 300mm, basically unusable. I'd shy away from the Tamron if this is a lens you expect to use a lot.