Any nation can do well with any base set of resources. If you have resources like mine it just means you'll have to spend some time paying to find trades. I 'bought' a trade circle that is the best I'll ever do. My base resources are gold + lead, and while many of my trade circle members could get better trades they choose not to because what they have is easier, it's still pretty good and I paid them when they were small and helped them grow.
Personal relationships >> What is optimal, quite often.
Also, at high NS levels most of your growth will be in the form of tech dealing; 18m a month is really nothing at high levels, no matter how bad your trade set might be.