Hi Allison, you have some beautifull pics in your gallery.
I have the Nikon version of the plastic 50mm f1.8, $90. Its light , fast, and sharp. I dont think of it as cheap, I think of it as a GEM! The only lens I have that is as sharp, maybe slightly sharper even is a $580 100mm Minolta macro.
Try setting your zoom lens to 50mm and see if you can work with that focal length comfortably. If so go for the 50 1.8, unless you can spring for the 50 1.4.
As for flash look at Vivitar 283. about $70, and powerfull enough to be bounced from an umbrella. I use sunpack 383 flash (similar, but not as sturdy as viv 283), even though i have the top of the line Nikon flash. ( still havent put batteries in it.)
Also look into a flip flash type of bracket. This will keep the flash above the lens when you shoot verticly.
Sorry for being breif, been knocked off the net several times trying to post here.
Good luck,
Mark.