HI Ryan,
Can you narrow the scope of your question? Without any context of your business needs, it's really hard to answer this. Of course the spec includes all fields that are "required" to complete a successful bid request/response transaction. And there are also "recommended" fields, but other than that, most is "optional" for the very reason that they are useful to some, but not all.
So, what do you "need" for your business strategy?
Cheers,
Jonathan