I plan on joining the Marine corps within the next year or two.

Nice! I'm currently in the process of enlisting for the Navy! I can't wait to get out there and serve with all the brave men and women defending our country (though Marines are a bit more hardcore than a Naval engineer. :p).

What size is the gun bag? And how much for the bag and sling?

On a slightly different note, what brands are most reliable? I've been looking at mostly Condor stuff, but I hear they're not very high quality. I'd prefer to get pieces that will last forever so I only have to buy once, rather than buying cheap pieces over and over.

Here's my abridged list at present:
Condor chest/hydro
Gryffon dragon spine belt
Propper A-TACS
PIG FDT gloves
Under Armor boots
Bravo PJ helmet

Any if these appalling enough to warrant substitution?

Like I said, I know what I WILL be getting (I've got pretty much everything picked out on airsoftgi.com), I'm just looking for feedback (not necessarily a checklist) to see what stuff I'll get FIRST.

That's the impression I got. It didn't sound like it was two guys, "Hey, let's take KIA photos and post them online!" They were at an event emulating the procedures of a real operation. Maybe some thought it was in poor taste, but to paraphrase what was said above, "Emulation is the highest form of admiration." If they want to act like real soldiers, that's fine with me, as long as they aren't being dicks about it.

Greetings! Long story short, I'm pretty new to airsoft, but I'd like to start acquiring gear. I'm familiar with the type of gear I want to get, but I don't know what kind of stuff is highest priority. Right now I've got a gun and a mask. I trust I'll get it all eventually, but what would y'all recommend l pick up first? Boots, camo, sidearm?

EDIT: As for where I'll be playing, right now I'm just at Fightertown, but I anticipate taking part in the long-form field games. From everyone's feedback, I think that boots, gloves, and utility belt would be a good start, and I can add the BDUs (I'm looking at A-TACS) once I reach full functionality.  After that, I'd start adding more mil-sim pieces, like goggles/helmet/balaclava, radio, plate carrier, etc.

Anyways, is all the stuff around here officially organized, or do people ever put together impromptu skirmishes in the "wilderness"?

Funny you should mention this when you did. The day you posted was the (free) Crossfire game up on the rim. I probably wouldn't call that "impromptu," as it was planned months in advance, and had National Forest permits and whatnot, but it was "wilderness." Alas, I could not attend, as my transportation is currently close to kaput.

If you're a member of the Airsoft Arizona facebook group, that's a great resource to connect with people and plan stuff. In fact, it seems we're organizing some kind of impromptu super-game at Fightertown some time in October, which I may or may not actually be able to attend.

Definitely got the bug for it, though I'll be needing a new rifle...

I know what you mean! I've been itching to play for a while, but circumstances have been restrictive lately.

Check out airsoftgi.com. They've got loads of products, coupons, and new deals every week. I got my first gun there, and I couldn't have been happier with their service.

See you on the field!