On average you should allocate the following:

AEG - $500
Battery - $50
Charger - $75
Magazines - $=Amount needed x $60
Load Bearing gear / Tac Vest = $120
Case - $20
Goggles / eye protection - $30

OPTIONAL
Tac Light - $50
Laser - $50
Red dot sight - $200
BDU - $=different patterns x $50