First off, I'd like to say "THANK YOU" for an intelligent, grammatically correct, (reasonably) insightful introduction. We don't get enough of this from the "fresh meat".
Also, for posting in the noob section, so you don't get excessively flamed for a new poster.
Second off, people are not likely to help you purchase a decent gun. As you probably read through the thread, a common element for noobs is to GET AGE VERIFIED (AV'ed). If you're 18+, this will be a painless process. Also, please fill out your profile.
Thirdly, if you live in an urban area, DO NOT HAVE BACKYARD WARS - you will likely alarm your neighbours, and cops will usually show up armed for bear when a gun is involved in an incident report. If you live in a rural area and still want to have backyard wars, DO IT OUT OF SIGHT OF PUBLIC VIEW - again, in the event that someone spots you running around with a gun shooting at others. Also, play safe - wear full eye protection, such as paintball or ballistic goggles. Worker's safety glasses, prescription glasses, sunglasses, etc. are NOT recommended - a BB at speed will take any of those out pretty quickly, and then you can say hello to the surgeon attempting to save your eyesight.
To your questions: TM and CA are generally considered "the gold standard", although other manufacturers have greatly closed the gap. For example, VFC and G&P are both great manufacturers, and their costs run about the same as TM and CA. There are lots of options out there, even more once you're AV'ed and have access to the buy & sell section of this forum.
Batteries - pretty much anything will do, as long as it fits your battery compartment. An 8.4V or 9.6V battery running 1100 mAH to 1600 mAH will run most of the day. They're available from a number of different makers, so pick what you want.
BBs - BB Bastards are the current "gold standard" - double polished, tight tolerances, consistent manufacture, and available in a wide range of weights. However, most BBs from a reputable maker will work for your application. The only caveat is STAY AWAY from the Walmart/Canadian Tire crapsoft BBs - they're only good for one thing... messing up your gun at a record rate.
Welcome to the forum. Read lots. Have fun, and play safe.