Soldato
50mm is a no-brainer, at least on Canon - the plastic fantastic is about £80, f1.8 and performs fantastically well. I'd imagine there's a Nikon equivalent.
35mm is a bit more flexible on a crop body, but you need a big aperture to give you the same subject/background separation as a 50mm f1.8. Unfortunately there's no big aperture 35mm on the market in the same price range as the 50mm.
Get a 50mm for sure, they're fun to use.
40mm pancake is also quite nice not as fast but sharp