Check out dashcamtalk.com. The forums are a good place to learn and ask questions. You'll probably want a Starvis 2 sensor at this point but I don't know of many under your price limit. Lots to consider from things like parking mode, power options, even head unit location on some. I'm personally partial to Viofo, Street Guardian, Thinkware, and Blackvue, but every company has bad units. Some of the company reps from dashcam companies even hang out on that site.
Blackboxmycar.com has some good deals on packages and accessories too. The guys that run that site are helpful and know their stuff.