I really liked the composition, processing, and really just everything about number 13. That's a seriously great shot.
#7(2) also stands out. Nice use of symmetry.
I personally would have focused a little closer to the broken piano key in #1, or used a more narrow aperture to include it in focus. All of the hard lines in the image kinda lead to it, but the sharpest focus is about 8 keys in front of it.
The window frame borders in #4 are fine. It works well with the tree in framing the house.
12 has a crooked horizon
Otherwise, all pretty solid stuff. As far as lenses go, I swear by the Sigma 10-20mm F3.5. It's very often the only lens I use. It's really sharp, and brings out awesome color. It's also seriously tough. Mine was run over by a very large ATV and snapped off the body, but it still works and it's never let me down since.
I also recommend old manual focus lenses as a way to get high quality glass for cheap. There are a ton of old offbrand 135mm F2.8 primes, and some of them are of really high quality. I've owned both a Sears and a JC Penney branded one that were great lenses, neither of them cost more than $40. Just make sure you get one new enough to have an AI mount so your camera's meter will work.