Equipment exchange, the classifieds section to CGN. Essentially the place where all us degenerates spend all of our money.
As for building, I just want to say I think accuracy should be a little higher on your list. Alls fun with a reliable gun but if you can't hit sh!t you're going to end up going home unhappy. That being said any reliable rifle will be relatively accurate.
If building is what you're set on for a first rifle, any basic mil spec upper and lower will do just fine. I prefer spikes tactical as they can be had for good prices from quester and most forged milspec uppers and lowers are built by a select few manufacturing plants and then branded with said companies logo.
Focus your money on 3 key areas from most to least important: barrel, bolt carrier group, and trigger.
Barrel I usually go Daniel defence because their cold hammer forged barrels are incredibly reliable and long lasting as wel as accurate for most people's needs.
Bolt carrier groups: anything milspec, DD & LMT are my preferred brands for the non Gucci stuff such as nickle boron or titanium nitrate coatings.
Trigger: if you want a great trigger for a good price, I recommend to everyone the ALG ACT trigger, designed by bill geissele who makes some of the best triggers, but in a sub 100.00 price for a standard 2 stage trigger.
Other than that, buy whatever other parts you fancy and go from there. The only other recommendations I have for building is don't buy a POS optic, spend your money and get a good "never fail" optic like an aimpoint and get a professional gunsmith to mount your barrel to your upper and make sure they use the proper tools like a reaction rod. Some smiths use cheap upper receiver blocks and can sometimes damage the upper when torquing down your barrel nut, as did happen with my recent BCM upper.
Closing statement, if you've never owned an AR, I'd still take the advice of most and just buy a decent quality complete rifle like a DD, colt, BCM, or something of those likes. Building a rifle, especially in canada is NOT cheaper than buying a complete rifle but it is enjoyable and beneficial if you know what you're doing and you're as fussy about parts as I am.