The kit lenses are good enough for most occasions. Personally, I bought the 50mm because I could afford it and felt I needed a faster lens. f2.0 is much better than f5.6 at the longest end or even the f3.5 at the widest end of the 14-45mm. Actually, if you need lens speed than the 14-54 is also bad, since that is f3.5 at 50mm.
Since you are not sure, I think best is to start using your kit lenses. If you feel later that you need a new lens you WILL know which one to get. Ever since I got my 50mm I hardly use the 14-45mm zoom. Image quality is definitely much better, the 50mm is actually better than the 14-54 also, but if you are not used to primes, zooming = moving, i.e. using your feet, so before rushing to spend a lot of money on something you have to do a self analysis to find out what and how you shoot. However, if you are into flowers, close ups or macro than there is no question.
Only you can decide which one to get, but I think the best is to get some experience. Time will tell. Don't buy anything just because there are ppl here who say this and that.