I'm currently looking for a good mic too, I will let you know if I find a good quality mic for signing I know some microphone can be pretty expensive. microphone I bought for my camera was around $299 it was worth it it's really good quality and the audio sounds amazing!
I personally use the Shure SM58, which costs around 100 bucks, and it is great. It has a cardioid pattern and it's dynamic, making it perfect for recording what's in front of the mic and less background noise. It has a built-in pop filter and it is extremely robust. (There are videos of it being run over with a truck and still working afterwards.) If you buy one you'll need a XLR to USB Interface, both as adapter and to amplify the signal. If you want it easy, get the X2U Interface from Shure, it's been designed to be easy to plug in and use. The X2U costs around 120 bucks.
Also, there is a YouTube Channel named Podcastage. There are loads of very good mic reviews on there, I also had a look at those before I bought my SM58.
I have a Blue Snowball and I'm gonna admit it's really not that good, it was only £40 (about $50USD) but there isn't particularly a lot of difference between it and my old Microsoft Headset. On top of that, I have to spend ages Audacity editing the audio to make it somewhat video standard.
However I have heard good things about Samsung Microphones?