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I don't know... on a crop-sensor camera, 85mm is awfully long. To do full head and torso shots requires you to stand almost across the room. For someone just starting out, it may be a little tough to handle. I might consider the Sigma 50mm/1.4 EX DG HSM... the *old* version. It's a very good lens, fairly sharp wide open, and has nice bokeh and it's only $400 on Amazon.
I think your choices are pretty clear. 50mm (either Nikon 50mm 1.8 or 1.4G, or Sigma EX 50 1.4)60mm 2.8 Micro Nikon85mm (Nikon 1.8G)I personally think the 85mm serves you the best. It's probably the best lens of the bunch, plenty of speed, and though it's a little long, in reality shooting portraits at an equiv of 130mm is just fine (see all the people recommending the 135mm F2 DC).
I recently bought the D5300 with the 18-140mm lens. What lens would you recommend for portrait on a budget of $600?