I agree with Curo in that you should go with a King Arms or WE M4 AEG. They're both about $250, great out of the box quality, and really easy to upgrade. Personally I would go with the WE M4 AEG, mainly because I own one and they are super easy to upgrade (fully TM compatible). I have mine done to the tits now with Lonex internals and its a monster if a gun. Owned it for a year now and put well over 10,000 rounds through it and I just now stripped a spur gear. Comes to show what you can get out of them.
Guardians of Asgaard
"The judge meeting is arranged for terrorist." - G&P Laser Product
Primary - Z-Custom VFC ZTW
LifeLine - TM Glock G18C