Roughly about a grand. I'm in the same boat you are, and I've been doing some calculations
$700 for gun and accessories (package)
$60 for batteries and charger
$200 gear (I'm probably just doing basic BDU's, goggles, and a vest with lots of pouches)
$15 for a sling probably
Some stuff I haven't thought about yet: water, footwear..
So $1000 is average.