I'd recommend anything that Futaba currently makes. The GY 240 can be had a HeliHut.com for $95.
Lots of local guys are using the Century P2000 $84.95 at Heli-world.com and having great success.
The CSM 360 and up gyros are very good too.
If you can spend the money the Futaba GY401 w/9253 digital servo combo will take you from beginner to 3D pro but it's $200 at helihut.com +$10 shipping. Gyro alone is $140.