For $45 your options are going to be rather limited, and most cards in that range are going to be in the same general ball park of performance. Note that with 2GB of ram, and older duel core CPU, and a $45 GPU you are not going to play games much above the most basic of settings. Even older games are going to struggle, and some newer ones may not play at all.
I am afraid that it is time to save up some money to get a newer system. As Konnefke said, a modern AMD APU based system should have enough kick to play games at a basic level until you can afford a GPU. That may be the way to go at this point.