On my D300, I found the 17-55mm f/2.8 and 70-200mm f/2.8 VR (rent) to be sufficient for anything. I sold my WA Tamron because I found myself using it the least.
I wouldn't bother with the 50mm. Spend the $100 on more memory cards, better filters, or an extra battery. Those will serve you better in the long run.
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