[Ash]

Your 40mm lens will serve you well. It is a sharp and compact lens suited to many applications.
The kit lens really is an f/8 and be there type of wide-normal zoom. The 40/2.8 is a lot more versatile in low light situations, useable from f/2.8 and gives more artistic results on account of its shallower depth of field. Start there, and work out your focal length deficiencies and desires before splurging out on more lenses.