If it's your first AR, my recommendation would be to just use the standard trigger if your AR is going to be an M4-gery or other "tactical" style, or used for 3 gun, etc, at least until you get used to the platform and know better what you want and what the gun will be used for.
If you gotta have a two stage trigger for a tactical style build, I would recommend the Geissele SSA, which claims to be the only two stage trigger that's as durable and reliable as the standard single stage.
I have an SSA coming in this week, took a while to find someone who had one in stock (prices on them have also increased 33% since introduction). I have also heard good things about the two stage triggers from LMT (I think only sold as part of a complete lower receiver) and Armalite when used in tactical style guns (remember that reliability and durability is more important here). Conversely, I have heard that the Rock River two stage is not too durable, though I have a RR tuned by White Oak Armament, but it's on my SPR-style AR, and doesn't see high round counts. I don't know if the tuning makes any difference other than the feel.
If it's a precision competition gun of some sort, I have heard the "best" is apparently the Geissele hi-speed. Rainier Arms sells them with the springs for all three pull weights for the same price as other places charge for only one pull weight. I have also heard good things about the JP Rifles two stage.