No such thing... Nikon doesn't make a prime lens with the tagline "suitable for newbies".
You buy the lens with the focal length that is suitable for the photo(s) that you are going to take.
A lot of people recommend 50mm f/1.8, because it's the cheapest prime lens that Nikon makes.
So that "gets you started" in the prime lens area.
50mm f/1.8 gives 'normal' field of view on a film SLR or full-frame DSLR, hence that's what made it so popular (and consequently brought down prices).
On a cropped DSLR (like D90 is), 50mm gives field of view equiv to 75mm on film SLR.
If you have the kit lens with your D90, set it to 50mm and don't turn the zoom ring. Is that a comfortable focal length? If so, then go ahead to get the 50mm f/1.8 if you so wish.