I ended up in the top 20 for one, top 40 for another and top 60 for another of the ranked battleground categories, all in the same character.

I got 3 mails, each one with a yellow gear and a blue geode.

So, unless anyone have any other experience, I would say that as long as u end up at the leadership board for each category u will get a yellow reward regardless if you are ranked 1 or 100.

Cheers!