Considering your budget, second hand seems to be the option. You could find a 28mm 1.8 USM, a 24mm non USM, or even the 28mm 2.8 non USM. For 100$ more you could have them new.
I would not recommend the 14mm, since these are extremely difficult lenses to use. Anything under 24mm is less than universal, the extreme angle of view makes it very challenging to compose an interesting image. If you are not used to wide angles, I would highly recommend that you try something between 24-35mm to start with. Extreme wide angles (20mm and shorter) are somehow specialized lenses useful when you have no other choice. I do a lot of architecture and interior photography, were wide angles are standard lenses; the shortest I use is the 17mm, only in a few occasions would I have needed a shorter lens. One of the rules I always stick with is : take a lens as short as you NEED but as long as you CAN.
Try if you can to rent a 14mm, you will quickly realize how difficult it is to compose a clean image in most situations.