Hey, glad to see another member from B.C!
When you turn 18,introduce yourself onto Op-for / BCAC forums, and sign up for a game there. I suggest before buying a rifle, you wait, and go to a game. Hold, fondle, perhaps shoot some rifles, and see what you like best!
Now, as you're turning 18 very soon, I would advise you to wait on the G&G rifle. Age verification opens a whole world or goodies that would be 5x better, and there are some great deals in there.
For your first game, I would suggest renting a rifle, and perhaps see if you can also rent some sort of chest rig. You don't need full gear, but once you figure out what you want, gear is half the fun!
Headsets, and push to talks (PTT) can be found on various websites, depening on your radios. Try Redwolfairsoft.com, airsoftgear.ca( Run by Op-for Admin ), evike.com etc etc.
Also, for long games, it depends on what you consider long. But I'll try to give you a generalization.
-Sufficient batteries to last the day
-comfortable, functioning gear
Things like that. Of course, as you venture more into milsim, and hard core impressions, there is alot more people bring/use.