I'll let my first answer stand as I wouldn't want a change to it to receive votes which this answer might not warrant. Secondly, I cannot comment to help others in their process as I have a rep of 41 at time of writing...
Before seeing the hints today, I thought: "Well, the I Ching is way too obvious and much too obscure to be the answer."
Coupled with the fact that I'm quite apt at self-fulfilling prophecies, it could not be the I Ching as I specifically twisted concepts to fit my needs.
I then thought that the answer could very well be
Hexagram or Hexagrams
This would definitely validate the duality prominent in the use of 'I' and 'we' in the riddle, although I would be left with the same task of making the prose fit my argument: another self-fulfilling prophecy, ad nauseum.
Upon seeing the hints, I'm not so sure...
Five: You might need some of my kind to finally beat him.
Three: One of the others uses my goods. He can't do his job without them.
So please bear with me as I explain why I think that the answer to this riddle is
The Chief Officers of a Company
Let me elaborate
"We're a team of six."
#6 CEO: Chief Executive Officer, technically this is Team Member # 6
The Head of the group, makes the final decision. The Boss.
"I'm a large open field,"
#1 CIO: Chief Information Officer.
Pun on data as data information is a huge field.
"many plots make me home."
#2 COO: Chief Operating Officer.
Got to be involved in many aspects of the business.
"I like signs, I collect them,"
#3 CMO: Chief Marketing Officer
Hint2: Three: One of the others uses my goods. He can't do his job without them.
Without information from the CMO, the CIO cannot do his job.
"and I like my books, I've written a lot in them."
#4 CFO: Chief Financial Officer.
This is the position who does all the number counting and statistics analysis.
"You might need my kind to be a champ."
#5 CTO - Chief Technical Officer
Team Member 5 in Hint 1 states that we may need his kind to beat him.
Who is the him that the riddles alludes to? user_194421? Probably. As you will require skills and techniques to solve this riddle.
This position needs to be able to draw from a wide range of resources to manage the productivity of the company.
"And this we are, so who are we?"
All of them at once.
So given the information from the riddle I think that answer is
Chief Officers of a Company
Could be helpful to some:
Links where differentiation of roles is explained.