Background noise depends on the recording environment. If you're in a room that's very hallow (no carpet on floors, very big and open area for example), you'll tend to have a reverberation of the vocals due to the ambiance of the room. You can block much of the background noise if you isolate the mic.
Example A below. (attached image)
Now you can also limit the amount of background noise by using a vocal gate plugin to silence out the parts where your not speaking. A good free plugin would be floorfish
http://www.digitalfishphones.com/main.php?item=2&subItem=5
Just utilize your favorite vocal software (like audacity) and apply this vst to your vocals. It's tedious but there are tutorials online on how to use noise gate plugins.
Now a good mic you have to be more specific, especially when considering the price. Are you looking for something like a condenser mic, a usb mic, a dynamic mic, etc? There are plenty of options you can go through to satisfy your needs.