You can control the ESCs using the receiver via Arduino. Check out this link https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=8&ved=0CFgQFjAH&url=http%3A%2F%2Frcarduino.blogspot.com%2F2012%2F04%2Fhow-to-read-multiple-rc-channels-draft.html&ei=srgJUpK4BsXv0gWIiYCgBw&usg=AFQjCNFHRDRwVBw1oqcIh22lU8OMPT4XNg&bvm=bv.50500085,d.d2k&cad=rja
I’ve taken the code from the above link to read the throttle, aileron, elevator, etc. signals from the receiver and then passed the appropriate PWM signals (using the Servo library) to the ESCs to control the motors. I can confirm that this is all doable with some effort and highly recommend it if you want to learn things like interrupts, PWM control, etc. You can also purchase the 10 dof sensor stick from hobbyking.com for just $30 (http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=26913)…with this sensor stick you will get 3 axis accelerometer and gyro, etc. using which you can try some PID algorithms to stabilize your quadcopter! If you have the time and are brave enough (!) you can even try to write a Kalman filter code to get the most optimal orientation of the quadcopter given that the angle calculated from the gyro tends to drift and the angle calculated from the accelerometer suffers from errors when the quadcopter is accelerating + errors due to measurement noise, etc (I’m trying to write such a code currently).
If you have receiver and transmitter pair, you can get the other parts (motors, propellors, esc, quadcopter frame, arduino, sensor stick, lipo) for < $250 if you buy from a website like hobbyking.com where the prices are quite low (located in India, I find this website most convenient for me but there may be some other website that is better suited for your location).
Sorry for the late reply and hope that you find my suggestions useful!