You will collect many more exotics than that over time... Best exo primary AR is Suros, best armour really depends on how you play your character. Obsidian Mind for example is one of the better Voidwalker helms, but is useless for a Sunsinger. Exo Bounties will randomely drop, some people believe they have a better chance of doing so if you collect several bounites at once, though I have not seen a difference myself.