Sometimes, it fells good to put personal touch by using manual prime lens. You are in control. Forget the buzzing autofocus, just you and the object :)
This is a manual lens (D -Lens) for DX Body (ie. D3100, D3200, so on) you have to adjust your focus manually. If you are fuss free type, you can go for the 50mm f/1.8 G which has built in internal autofocus motor
However, 50mm F/1.8D "become" autofocus for FX Body
This is the cheapest so far, other sellers may have cheaper lens price but with shocking shipping cost (cheeky bastards)
Tips:
Before you mount it on your DX camera, set the aperture ring to 22 and lock it (orange switch), you can thank me later LOL
WTB coherent english.