on 7BR and 8BR trade sets. In most cases, these trade rings will not be the most efficient for your nations. Doing the math shows that the more flexible 3BR, 4 BR, 5BR or Affluent Popluation/Fine Jewelry setups will almost certainly be a better option for your nation.
While more bonus resources seems like it would be better, it is not so. All bonus resources are not created equal - the goal is to have your net profits (income - expenses) be highest. The best bonus resources happen to be the ones that boost your population and income, as those improve your profits more than the bill saving resources do. Also, do not discount the base resources that go into these bonus sets