As you mentioned that you are happy to build something yourself (i also think this is more rewarding) the overall price will be less. Here is a suggestion for a nice goPro size quadcopter
X580 Frame - Its nice because it has landing legs and can fit a servo based gimbal directly (or a brushless gimbal with cable ties onto the mounting tubes)
Motors - You have two choises, both are very similar, our 850Kv motors, or 935Kv motors
ESC - For the above motors you will need 4x 20A ESC, but I would suggest our 4 in one ESC for ease of installation (we will have stock later this week)
Props - the 935Kv motor comes with props, but if you want to upgrade them I would recommend the 10x50 carbon reinforced props.
APM2.6 with Ublox GPS and Power Module (we should have more stock soon)
You can find out some more info of the arducopter platform at www.arducopter.co.uk
I would suggest a 3S or 4S Lipo battery ov about 3000-4000 mAh capacity
Hope that helps!