You can go to "Army Issue" in Port Credit, right near you, and get Age Verified..
During the year there's a nice place in Whitby (Google Whitby Airsoft) $10 entrance for all day. Legit.
*cough* there's something called google for finding "stores."
For guns it depends on what rifle you want to build, and your play style. It also depends on your budget of how much you want to spend.
Generally $500 is a good starting point.
Most common are M4 variants, and AK. You could go bullpup (AUGs, SIGS, etc.) Also support/DMR/Snipers.
Then you'll want to consider whether you want to go Eletric (AEG) or Gas (GBB).